Provide command (plus keyboard shortcut) to zoom (or focus + increase screen real estate) to panes such as Viewer and Plots

[juliasilge]

We are starting to gather some feature requests for the ability to zoom or otherwise give more screen real estate to our Positron-specific UI components like the Viewer, Plots, etc.

• https://github.com/posit-dev/positron/discussions/3746 outlines a request to have behavior like RStudio's "zoom plots", "zoom console", etc.
• https://github.com/posit-dev/positron/discussions/4154 outlines a request to have behavior like VS Code's workbench.action.focusFirstEditorGroup and workbench.action.focusSecondEditorGroup for the Viewer pane, to give the Viewer more screen real estate.

Both are needs for when you are working on a small screen and want to focus/zoom to one part of your workspace (like plots or the viewer), then back to another (like where you are writing code).

Let's consider what option makes the most sense for us to support this type of need.

[factorialmap]

RStudio has options for expanding panels that I use a lot, and some people have asked me how I do it so quickly. I don't know if it would be possible to apply this to Position but these shortcuts allow you to view elements in widescreen with great speed.

https://github.com/user-attachments/assets/6c1617fa-8e7c-48f8-8df7-e83f02ef8408