Add rslint-pragma to specify the source type of a file

[RDambrosio016]

I noticed this being talked about in a deno_lint issue, and i think it would work well (but sadly deno_lint cannot implement it efficiently since they would need a lossless lexer to run on the code first or parse the code twice). To get this to work for us we would simply have to refactor a couple of things:

• Make the core runner first run rslint_parser::tokenize
• Do some kind of preprocessing by going through each comment token and checking its source
• If a source type is specified then get that, or get the default one (script for .js, module for .mjs)
• Make a new rslint_parser::TokenSource
• Spawn an appropriate parser with new_module or new
• Use the appropriate parser function from the syntax::program module and get the parser events and process then with a new LosslessTreeSink (theres instructions here on how it works)

There would be no need to run through a proper directive parser, just check for rslint-pragma script and rslint-pragma module.