Move to ESLint and Prettier

[jasongrout]

This is a WIP PR to move to eslint and prettier for code linting.

[jtpio]

Another thing that would be great to do would be to unify the naming of variables, function parameters and so on, to have a consistent style.

At the moment, the TypeScript code uses a mix of camel case and snake case.

This could also be done in a separate PR (if so we can open a new issue). And it can be a quite big breaking change if the API (save_changes as an example) is also modified.

[jasongrout]

The one thing left is a failing test in web3, which exposes that we are not consistent at all in how we define and use our widget manager display_view function. Let's talk about this tomorrow.

[vidartf]

Current failing lints will be fixed in a follow-up PR to avoid further conflicts :)