feat: support keep top language

[leavesster]

1. add top parameter to keep top number languages.
2. add EN and CH README.
3. remove duplicate parameters.

[codecov]

Codecov Report

Merging #176 into master will decrease coverage by 0.23%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master     #176      +/-   ##
==========================================
- Coverage   94.75%   94.51%   -0.24%     
==========================================
  Files          15       15              
  Lines         381      383       +2     
  Branches      114      115       +1     
==========================================
+ Hits          361      362       +1     
- Misses         16       17       +1     
  Partials        4        4              

Impacted Files	Coverage Δ
api/top-langs.js	100.00% <ø> (ø)
src/renderTopLanguages.js	97.22% <50.00%> (-2.78%)	⬇️

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[anuraghazra]

Hi @leavesster we already have hiding specific languages option implemented in #150 so hiding top languages is not needed anymore. we previously had "hide_langs_below" option to hide langs below certain threshold but we already deprecated it for the same reason.

[leavesster]

I just want to keep top languages no matter what language they are. I know hide specific languages can do it too, I just want to make it more simple, but it's true that top languages changes slow.