Migration to firefox-devtools org

Firefox DevTools wants to support the development of this extension. Joining forces with @hbenl, who will remain a maintainer, we'll continue with shared governance!

Apart from @hbenl and me, the Firefox DevTools team members that will be involved are @janodvarko and @jasonLaster.

**How will shared governance help this project?**

1. Keep the extension in sync with Firefox's debugger server, remote protocol changes and upcoming features (e.g. dfddc7a8134b3672fd9857f4c1d39a56a582ef02, 5f86bdbd2c27137e55f3bfd3352a95abb7a2cb6a, etc)
2. Simplify setup and integration with DevTools
3. Make this the official Firefox extension for VSCode, with proper branding (e.g. #81)
5. Do more joint outreach to spread the word about the extension and how to set up

**What's next?**

- [x] Transfer repo to https://github.com/firefox-devtools. _Owner: @hbenl (moving the repo)_
- [x] Make @hbenl and @jasonLaster, @janodvarko & @digitarald maintainers of that repo. _Owner: @digitarald (admin in `firefox-devtools`)_
- No need to update Copyright/License
- [x] Add Mozilla's `contributing.md`, `CODE_OF_CONDUCT.md`
- [x] Update references
- [x] VSCode extension marketplace
- [x] Update branding
- [x] New icon (@hbenl)
- [x] Updated description (@digitarald)
- [x] Shared publishing access
- [x] Create new publisher ID
- [x] Update publisher ID for current extension with support from the VSCode team. Owner @digitarald
- [x] Ship a new release (@hbenl)
- [ ] Announcement
- [ ] Blog post (@digitarald / @janodvarko)
- [ ] Update [MDN DevTools page](https://developer.mozilla.org/en-US/docs/Tools) (@digitarald)

Start by reviewing the unchecked Announcement items in this issue: the blog post and the MDN DevTools page update. Confirm the repository migration, branding, publisher, and release checklist items are already complete, then coordinate with the named owners before changing external content. Done means both announcement tasks are completed and the linked references accurately describe the extension.

Written by the indexing model from the issue text.