Add keyboard shortcut to Web IDE to toggle Markdown preview

Release notes

TBD

Problem to solve

Working with Markdown files in the Web IDE requires a mouse click on the Preview Markdown link in order to generate a preview of the page. Other IDEs map this to a keyboard shortcut so you don't have to take your fingers off the keyboard to quickly preview your content. Often this preview is presented side-by-side with the markdown file.

Proposal

As proposed in #22006 (closed), we should introduce a keyboard shortcut to toggle the Markdown preview as an iterative step to improve the preview experience.

• The keyboard shortcut most familiar would be CMD/CTRL + SHIFT + P
• This would only work on files ending in .md (when the Preview Markdown option is available)
• The shortcut would toggle the preview, so if you are looking at the source view, it opens the preview. If you're looking at the preview, it goes back to the source.
• This issue doesn't impact the functionality of how the Web IDE handles Markdown or enhance anything about the Preview itself. It's just a shortcut.
• The shortcut should be documented in the keyboard shortcut modal

Intended users

• Parker (Product Manager)
• Presley (Product Designer)
• Sasha (Software Developer)

User experience goal

The user should be able to preview their markdown file in the Web IDE using only keyboard input.

Open Questions

1. Is this keyboard shortcut available to be used?
2. Does this make sense to add to the Web IDE before the upcoming integration with Editor Lite?