feat(eslint-plugin): add prefer-for-of rule

[edsrzf]

This rule provides functionality equivalent to TSLint's prefer-for-of rule. Test cases are mostly taken from TSLint, but I added others that I thought of while implementing.

Note that this implementation still falls into palantir/tslint#2021, false positives on non-Arrays that are still indexable and have a length property, such as typed arrays. We'd need type-checking to do better than this.

This is the first attempt I've made at writing a lint, so bear that in mind. 😄

[bradzacher]

Few changes, but otherwise LGTM.

Note - also needs to add link to the rule doc in the README.md

[edsrzf]

Thanks for the review! Updated.

While updating the README I also noticed I have the option of using type information, which would allow us to fix palantir/tslint#2021. Would it be worth it?

[bradzacher]

Awesome work! LGTM

[bradzacher]

@edsrzf - you could use the type information if you want. I don't know how necessary that is immediately considering that is a bit of an edge case.
I would consider doing it as a separate PR, if anything.

[codecov]

Codecov Report

Merging #338 into master will decrease coverage by 0.09%.
The diff coverage is 92.45%.

@@            Coverage Diff            @@
##           master     #338     +/-   ##
=========================================
- Coverage   96.96%   96.87%   -0.1%     
=========================================
  Files          69       70      +1     
  Lines        2572     2625     +53     
  Branches      408      424     +16     
=========================================
+ Hits         2494     2543     +49     
- Misses         46       49      +3     
- Partials       32       33      +1

Impacted Files	Coverage Δ
packages/eslint-plugin/src/rules/prefer-for-of.ts	92.45% <92.45%> (ø)