Update syntax highlighters

[Rangi42]

Make sure these support all new keywords and tokens.

• https://github.com/DonaldHays/rgbds-vscode
• https://github.com/ISSOtm/sublime-RGBDS

Also consider simplifying sublime-RGBDS to understand context less, and just highlight tokens instead of trying to mark whole lines as erroneous. (That way it won't be so forwards-incompatible with slightly new updates, but will keep on highlighting the keywords and tokens it recognizes.)

[Rangi42]

Unrelated reminder: update rgbds-structs to use 1.0.0 when it's out (e.g. STRFIND instead of STRIN), and also try implementing its open issues (two currently).