UnturnedLexer module

[MoltonMontro]

Following up on #311, this adds a custom lexer for UnturnedDat files (.asset and .dat). There's a couple shortcomings, which I've added as comments within the lexer.

Notably, the rule for matching numbers doesn't match values like .1. This could be changed, but we may need separate rules for integers and floats (possibly GUIDs). Also – lists/dictionaries that don't require key-value pairs (e.g., CraftingBlacklistAsset supports listing GUIDs without a key) will see those values matched as keys.

Extensions can loaded locally from _extensions. Our custom lexer is unturned_lexer.py, and is usable within code-blocks with unturned. We could add other aliases such as unturnedasset, unturneddat, dat, etc. I've updated a couple code-blocks to use the lexer.

• https://unturned--322.org.readthedocs.build/en/322/assets/crafting-blacklist-asset.html
• https://unturned--322.org.readthedocs.build/en/322/assets/item-asset/gun-asset.html#attachment-caliber-uint16

[MoltonMontro]

Side note: we can adjust the colors of tokens. Either by just changing the token type used by a rule (since being accurate/consistent with other languages doesn't really matter here), adding custom CSS, or making a custom formatter.

[SDGNelson]

This is fantastic - great work! I'm still quite impressed that you did it with just regex.

As you mention, I agree it would be a good idea to have the "unturneddat"/"unturnedasset" language (more specific than "unturned") and playing around with the colors in future commits.