Allow toggling syntax highlighting on/off for the page from a right click on the textarea/similar

Sometimes I want the syntax highlighting, sometimes I would prefer it to just remain untouched; and usually the times where I want to make that decision are somewhat arbitrary and in the moment. It would be nice if I didn't have to 'reach far' to be able to toggle this; even better if it's not via the extension icon in the app bar because I already have way too many pinned open, and I would rather this 'fade into the background' except when I explicitly need it.

There's an extension called Markdown Toggle, and it seems to only show in the right-click context menu when I am clicking on a textarea or similar; but not when I right-click on a random section of the page. This feels like a nice compromise.

Potentially for GitHub textarea's in particular, there might also be an option to add a 'toggle syntax highlighting' button to the 'markdown toolbar' too:

No files, tests, or implementation entry points are named. Start by tracing how the extension registers textarea syntax highlighting and browser context-menu actions, then determine how the toggle should affect GitHub textareas and how its enabled state can be verified from the page.

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