feat(eslint-plugin): support type assertions in no-extra-parens rule

[webschik]

Fixes #12

[codecov]

Codecov Report

Merging #311 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #311      +/-   ##
==========================================
+ Coverage   97.14%   97.14%   +<.01%     
==========================================
  Files          73       74       +1     
  Lines        2868     2875       +7     
  Branches      473      473              
==========================================
+ Hits         2786     2793       +7     
  Misses         49       49              
  Partials       33       33

Impacted Files	Coverage Δ
...ackages/eslint-plugin/src/rules/no-extra-parens.ts	100% <100%> (ø)

[bradzacher]

In terms of documentation - do we just want to link to the ESLint documentation instead of copying it over here?
I know we've copied it in the past, but maybe if we just document our changes to the base rule, and link out it'd be cleaner for us?

Thoughts @typescript-eslint/core-team ?
If yes - we should fix it across the board (in a separate PR).

If no then this PR LGTM (apart from the one minor nit).

---

Great work @webschik.
👍 Figured out all the pieces to extending a base rule without any documentation.

[j-f1]

I’d say we should link to the original docs and describe how our rule differs.

[webschik]

@bradzacher , @j-f1 , I can update eslint-plugin/docs/rules/no-extra-parens.md file. Smth like

disallow unnecessary parentheses (no-extra-parens)

Rule Details

This rule extends the base eslint/no-extra-parens rule.
It supports all options and features of the base rule plus TS type assertions.

How to use

{
    // note you must disable the base rule as it can report incorrect errors
    "no-extra-parens": "off",
    "@typescript-eslint/no-extra-parens": ["error"]
}

Options

See eslint/no-extra-parens options.

[webschik]

@bradzacher , can we merge this PR?

[bradzacher]

Sorry @webschik - it got lost in my notifications.