Upgrade to @ethereumjs/eslint-config and lint

[cgewecke]

#148

NB: PR targets #152

Lints everything. Mostly automated fixes but have put the things done manually in a sequence of separate commits.

The meaningful config commits are:

• 002e886: package upgrade and initial config
• db45450: addition of files not enumerated by tsconfig
• 074994e: turn "no-unused-vars" rule off

The pre-commit hook works out of the box, it's great.

[cgewecke]

Small note about parserOptions... was getting an error complaining of files unreachable through the tsconfig similar to:

error: Parsing error: "parserOptions.project" has been set for @typescript-eslint/parser.
The file does not match your project config: unusedFile.ts.
The file must be included in at least one of the projects provided at unusedFile.ts:

Have followed the suggestions at typescript-eslint#parserOptions.project to add the browser folder files and webpack.config.js to the lint set.

[cgewecke]

There were 8 locations where prettier requires we insert a semicolon to prevent potential ASI failures. However eslint (correctly?) complains these are unnecessary - e.g. their views conflict.

Deferred to prettier in this case because otherwise its semi rule would need to be turned off. (Not sure this is the right thing though...)

[coveralls]

Coverage increased (+1.6%) to 76.195% when pulling 95acba1 on upgrade/eslint-config into b4d885b on master.

[holgerd77]

Whew, great, this could really be much quicker realized than I expected after my experiences with the monorepo battling. Cool! 😀

[cgewecke]

@holgerd77

I don't understand this sentence. Isn't the deactivated rule this mentioned rule from above?

Ah, actually every no-unused-var was being reported twice, once by the "regular" eslint rule, and once by @typescript-eslint/no-unused-var.

The latter is more permissive - if you rename the var with an _ prefix it goes quiet.