More checker features

[kaleidawave]

• Class hoisting and now using as internal definition (in overrides.d.ts).
• Package imports (looking in node_modules). Uses simple_json_parser
• Change to FunctionType for effects
• More mapped type things
• Class static blocks
• Template literal type annotations resolving (using existing addition mechanism)
• Literal type experiment
• Test for comments as type annotations (added back in Add basic comments-as-types for variables and function parameters #57)
• Extends super call (only for auto constructors)
• Fix performance-and-size test
• Now up to 197 tests passing 🎉

(Could have been done here), but will do in later PRs

• Merging .d.ts files with their package content
• Actual function hoisting (only implemented class types here)
• Object constraint problems
• Mapped type property value specialisation and remove (needed for Pick)
• Checking template literal type annotation & specialisation (e.g. `Hello ${T}` :> "Hello Ben" which is "Hello " + T :> "Hello Ben")

[kaleidawave]

Got to the bottom of why .github/workflows/performance-and-size.yml wasn't working. Turns out scc .\demo.ts wasn't working on Linux (Windows filepaths are borkt). Fixed now!