track: Lexer tracking issue

[ThePuzzlemaker]

This is a tracking issue for the lexer, contained within calypso_parsing::lexer. This is marked as blocking as it is impossible for Calypso to function without the lexer fully functioning.

Updates

• 12/12/20: The lexer has been split into multiple files (and clippy::pedantic has been enabled for calypso_parsing) as of d9d988c.
• 3/24/21: The lexer is mostly done, but is purposefully incomplete. Literals are pretty much done though.
• 8/5/21: Rewrote lexer using logos. Less expressive error handling, but still pretty effective.

Checklist

• Lexer debug interface (int lex)
• Basic tokens (e.g. <, +=, ...) -- partially done, but mostly disabled for productivity:tm:
• Keywords
• Identifiers
• Literals
  • Character literals
  • String literals
  • Number literals
    • Signed integer literals
    • Unsigned integer literals
    • Float literals
• Testing
  • Diagnostics
  • Correct operation