Upgrade manifest to v3

When the extension is loaded, it will show this warning in the console:

Manifest version 2 is deprecated, and support will be removed in 2023. See https://developer.chrome.com/blog/mv2-transition/ for more details.

• https://developer.chrome.com/blog/mv2-transition/
• https://developer.chrome.com/docs/extensions/mv3/intro/mv3-migration/

Waiting for the dependencies to support manifest 3 before migrating. Currently watching https://github.com/abhijithvijayan/web-extension-starter/issues/66