Update keywords list

[J3RN]

I noticed that "as" was missing from the list, and decided to update the whole list while I was there. This change makes the x-keywords list match the keyword token list in the Gleam parser.

I also alphabetized the list such that it matches the parser.

Changes:

• Add "as"
• Add "if"
• Add "todo"
• Remove "tuple"
• Alphabetization