xtask

[WillLillis]

• Add xtask to the project, including:
  • A command to regenerate the .asm-lsp.toml schema
  • A step to make sure the schema is up to date in CI
  • Shamelessly ripped from feat: generate schema for config file ribru17/ts_query_ls#60, thanks @ribru17!
• Move the regenerate logic into xtask
  • This could be polished up a bit, but for now it's fine