Manifest v3 examples needed

[erosman]

New MV3 examples shall be created and added to the current examples.

[GeorgeDaris]

I was about to ask about this. Can't wait to learn more about mv3.

[notshriram]

Still no updates about this? It's been quite some time since support was added for mv3 in firefox.

[Huluk]

I wanted to start writing my first Firefox plugin today, but motivation dropped a fair bit when I discovered that there is no documentation for the freshest tech. I spent 3 hours trying to write a v3 manifest so far – no success.

[Rob--W]

Re-opening. While #526 adds three MV3 examples, we still need more examples to demonstrate the differences between MV2 and MV3, notably in the background key.

PR #526 includes the following parts that are specific to MV3, along with a demo of the declarativeNetRequest API:

• action (successor to browser_action)
• host_permissions and how to request them.
• optional_host_permissions (not implemented in Firefox yet) and optional_permissions.
• web_accessible_resources (new syntax in MV3).
• Using the action and options_ui APIs to have a place to run logic other than the background script (since the background key is not cross-browser yet; Chrome and Safari supports background.service_worker, Firefox and Safari supports background.scripts, but there is no key that is supported by all).
• Not explicitly mentioned in the README, but the examples shows how to easily polyfill browser in MV3 in Chrome (basically globalThis.browser = chrome; when browser is undefined)