Add an update check to nimbus-devtools

[brennie]

We can check the latest release from the GitHub API: https://docs.github.com/en/rest/releases/releases?apiVersion=2022-11-28#get-the-latest-release

We should do this once per session at most. We can then add a toast (i.e., in extension) when the user opens nimbus devtools prompting them to update. We could also optionally do a browser notification.

This feature should have a toggle to disable it.