Re-inject site scripts when background process wakes up from idle

[jdgarcia]

https://gitkraken.atlassian.net/browse/GKDOTDEV-612

Repro steps are super easy (recommend Firefox since it's easy to tell if the background script is running)

1. In Firefox, open about:debugging#/runtime/this-firefox
2. don't interact with the extension (don't open launchpad, don't go to provider websites), and after a minute or two, the browser will turn off the background script
3. open a link to a repo/PR/commit/etc. the background script will wake up and re-inject the scripts but the page will have already loaded so it won't have the injected buttons

[gitkrakel]

I confirmed this will re-inject into existing tabs if other tabs are already running the script.

Technically this isn't a problem for the user since all injection scripts are written to remove existing injections each time it renders, but it's an efficiency problem since there will be new event listeners each time the script is injected.