feat(eslint-plugin): [no-empty-func] private/protected construct

[a-tarasyuk]

Fixes #1178

[typescript-eslint]

Thanks for the PR, @a-tarasyuk!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

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[codecov]

Codecov Report

Merging #1267 into master will decrease coverage by <.01%.
The diff coverage is 82.35%.

@@            Coverage Diff             @@
##           master    #1267      +/-   ##
==========================================
- Coverage   94.07%   94.06%   -0.01%     
==========================================
  Files         131      131              
  Lines        5737     5746       +9     
  Branches     1616     1618       +2     
==========================================
+ Hits         5397     5405       +8     
+ Misses        184      183       -1     
- Partials      156      158       +2

Impacted Files	Coverage Δ
...kages/eslint-plugin/src/rules/no-empty-function.ts	88.88% <82.35%> (ø)	⬆️

[bradzacher]

A few nits, otherwise LGTM - thanks