Enable eslint and solhint

[Amxx]

To replicate @openzeppelin/contracts linting, we should enable eslint and solhint with the same settings.

The checks/eslint-solhint branch includes some of the requested changes. However some issues remain:

• Disable solhint checks on the vendor contract
  • the glob approach used for prettier doesn't apply
  • Make sure this also applies to lint-staged
• copy vs link to config files in the submodule

[arr00]

Fixed in #39