ESLint plugin redesign

[wcjohnson]

ESLint has greatly expanded its extensibility, opening up the possibility of implementing LightScript linting on a purely plug-in basis without hacks.

See:

https://eslint.org/docs/developer-guide/working-with-custom-parsers

At minimum we would probably have to fork eslint-scope and update it to handle LightScript scopes. LightScript node types can also be registered for traversal.

• ESLint has strict requirements that all nodes must have a Loc property.
• ESlint uses ESTree AST, so lightscript/parser will have to cooperate with the estree plugin.

[wcjohnson]

This has been done in 4.0 with astonishing success. Already available on NPM under @lightscript/eslint-plugin