Update Enum names, improve enum member names, and add related suggestion

[Lexyth]

• Changed the grammatical number of all enum names to be singular.
• Removed the enum names from their members, (e.g.: Tile.TILE_BRICK -> Tile.BRICK).
• Added a suggestion for the reader to use singular case for enum names.

[Lexyth]

I'm a bit lost.
I don't think this error was caused by anything in my PR specifically, so I've just been waiting for someone to approve/reject it. But now it's been a while and my other PRs from the same day have been merged already, so it feels like that error is blocking the process here.
If someone could tell me whether I have to do something, it'd be appreciated.

[dalexeev]

Looks good to me. Please try to rebase the branch to fix the failed test.

[skyace65]

Thanks! Don't worry about that build issue, it was the URL checker, you didn't cause the problem and we don't run it on every PR now.

[Lexyth]

Oh, good.
I was pretty sure I didn't cause it, since I didn't touch anything URL related, nor change anything escape-codey or similar, but you never know.
I think I tried rerunning the action and got the same result, but maybe I just misremember that. Will try to rebase if it happens again on another PR.