docs: Split interactive docs section into subpages

[joelostblom]

As discussed in https://github.com/vega/altair/issues/3500 with @dangotbanned

New look:

[dangotbanned]

FYI I was about to try building the docs, but needed this merged https://github.com/vega/altair/pull/3560

vl_convert stubs untracked


[dangotbanned]

45ffa94 (#3561) fixed those pages not diplaying any charts.

sphinx shouting at me

```log C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\bindings_widgets.rst:45 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\bindings_widgets.rst:80 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\bindings_widgets.rst:120 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\bindings_widgets.rst:169 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\bindings_widgets.rst:202 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\bindings_widgets.rst:253 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\bindings_widgets.rst:276 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\bindings_widgets.rst:305 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\bindings_widgets.rst:323 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\bindings_widgets.rst:339 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\bindings_widgets.rst:373 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\expressions.rst:22 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\expressions.rst:55 Code Execution failed:NameError: name 'chart' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\expressions.rst:64 Code Execution failed:NameError: name 'chart' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\expressions.rst:70 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\expressions.rst:94 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\expressions.rst:117 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) C:\Users\danie\AppData\Local\hatch\env\virtual\altair\CXM7NV9I\doc\Lib\site-packages\sphinxext_altair\altairplot.py:261: UserWarning: altair-plot: C:\Users\danie\Documents\GitHub\altair\doc\user_guide\interactions\expressions.rst:149 Code Execution failed:NameError: name 'alt' is not defined warnings.warn(message, stacklevel=1) ```

[joelostblom]

Thank you! Merging