codemirror themes

[felixroos]

switchable themes, using https://uiwjs.github.io/react-codemirror/#/theme/home . backgrounds need special treatment, because the edtor must be transparent to let the drawings through

[felixroos]

Started with this:

So far only the codemirror theme changes, which clashes with the fixed colorization of header / footer. It would be nice if the non editor ui elements would be colorized using colors from the theme so everything fits together. It could even colorize the docs too.

• saving the selected theme to local storage, possibly also in the code (or else viz might look bad when sharing)

[felixroos]

light themes looks particularly bad

[felixroos]

no theme is also a theme: https://github.com/uiwjs/react-codemirror/issues/431

[felixroos]

ref https://github.com/uiwjs/react-codemirror/issues/457