feat(eslint-plugin): [no-type-alias] handle conditional types

[otofu-square]

Fixes #949

• add allowConditionalTypes option to no-type-alias rule
• test
• docs

[typescript-eslint]

Thanks for the PR, @otofu-square!

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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[bradzacher]

LGTM - thanks for this

[codecov]

Codecov Report

Merging #953 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #953      +/-   ##
==========================================
+ Coverage   94.14%   94.14%   +<.01%     
==========================================
  Files         124      124              
  Lines        5330     5333       +3     
  Branches     1489     1491       +2     
==========================================
+ Hits         5018     5021       +3     
  Misses        178      178              
  Partials      134      134

Impacted Files	Coverage Δ
packages/eslint-plugin/src/rules/no-type-alias.ts	95.08% <100%> (+0.25%)	⬆️