Pick code style conventions

[Rangi42]

Since we manually edit the HTML, CSS, and JS here, we should decide on a preferred code style (indentation, line length, JS features to use/avoid, etc). The ones that can be enforced by Prettier should be added to .prettierrc, and other conventions should be documented in a STYLE.md file.

[SelvinPL]

"printWidth": 100, give it 150 per line - we are not living in middle ages with 1024x768 resolution
also when i can back to work? with such changes you are not making it easy ...

[Rangi42]

Sorry, I'm done now, that was the last of my broad auto-format changes. (I should really be focusing on work-work, lol.)

Can we compromise on 120? Screens/windows aren't always wide enough for 150. (I'm used to 100 from rgbds source.)

[SelvinPL]

120 fixes some strangly looking <a/>, fair enough
could you do?

I'm thinking about about some small changes .. like menu and button size (I think they are too small padding: 4px 16px shoudl fix it also then menubar should be changed from 21 to 24xp)

So I would love if you would do 120 change and I would tweak those stuff

[Rangi42]

Okay! I eventually want to do a broader UI reconsideration/refactor, but should not let myself get distracted by that right now, and if you end up accomplishing what's needed anyway, then great. :)