Feature/rework using plugin template

[DanielHudson2]

• Incorporated config files from new plugin template
• Removed settings.js as it was for the old settings screen
• Added main Plugin class where other classes are initialised
• Rather than calling several classes from the 'init' hook in the main plugin file classes now call a separate init function within their setup function if necessary
• Added more documentation of returns on functions

[brettsmason]

Not sure we need css and js checking in Orbit, as we dont currently use either.
The PHP run could be composer run lint instead, then no need to use node. Though perhaps it was just in case for future?

[DanielHudson2]

I wasn't sure on this but thought it could be good as a future thing, though we don't have any plans with orbit that would likely involve this right now so it could always just be added when needed

[DanielHudson2]

I have removed the css and js checking and node for now, we'll re-review down the line if the need for it arises rather than having it in for no reason currently

[brettsmason]

Overall looks great thanks @DanielHudson2. I had one query on Lefthook - I left a comment.
GitHub Actions probably need updating too, but thats for another PR when we have settled on a test suite.