Manifest v3 rebase

[kawazoe]

Rebuild of the initial manifest-v3 branch to include all the most recent changes. Since the original branch was non-functional, I haven't tested this new revision either. This PR will give us a stable place to work on, add new features, and mostly make future code review simpler by limiting the scope of changes.

Note:
@ish- initially asked for a rebase in #4 but after doing the merge, I'm not so sure this was a good idea. GitHub won't be able to handle the merge automatically. I propose this should be the last rebase we do on this branch and everything else gets done via cherry-picks and merges.

Followup:
The next PR will be about standardizing the code style and making sure that everyone can edit the code no matter their IDE or OS. After that, I'll be good to go for a fix.

[ish-]

do you actualy need .idea folder here? )

[kawazoe]

do you actualy need .idea folder here? )

Not necessarily. Alternatively, I could add the whole .idea folder to the gitignore file instead.

This is just useful for sharing project level settings with other people who might be using this IDE (like code style rules), a bit like the .vscode folder, if that's what you use. Ignoring the whole folder would prevent that.

EDIT: As a note, I plan to add an editorconfig file in my next PR to try to automate the code styling work a bit, but it might not support everything that WebStorm or VSCode would. This is a good example of where those additional configs would go if we keep the folder.

EDIT2: I managed to get all of the WebStorm's settings I needed into the editorconfig file, so it's totally fine to gitignore the whole folder if you want.

[kawazoe]

@ish- I know this is already merged, but could you take a look at my previous reply?

[ish-]

@kawazoe feel free about it, it's not that serious ж)