Restructure lexer/parser folder structure

[TwitchBronBron]

We currently support parsing brs/bs and xml files. However, now that the file api has been merged, we may start adding additional parsing (manifest, translation, generic json, etc).

We should restructure the lexer/parser folder structure so that they make more sense within the context of a project with many parsers.

Not sure the right place to put them, but perhaps something like this, where we migrate all of the file-specific stuff into a file-type-specific folder:

• files/
  • brs/
    • parser/
    • lexer/
    • BrsFile.ts
  • xml/
    • parser/
    • XmlFile.ts
  • manifest/
    • parser/
    • ManifestFile.ts