Improve developer experience for parse tree extension updates

[pokey]

The problem

The extension sandbox can end up with an old version of an extension (especially the parse-tree extension), and it isn't clear that this has happened or what to do about it.

The solution

• [ ] Add --force argument to https://github.com/cursorless-dev/cursorless/blob/660a961154f6a3cbd5246f1a1015304b697f8e2f/src/test/initLaunchSandbox.ts#L24-L31 to force update on running yarn init-launch-sandbox
• [ ] Add file that tracks minimum version of parse-tree extension (just add field to package.json?)
• [ ] Check version of extension on extension load if we're in development mode, and if so fail, linking to instructions for update
• [ ] Add update instructions to documentation (yarn init-launch-sandbox)