feat: bump pre version

[aa900031]

Add bump pre version, It can set with arguments: --premajor, --preminor, --prepatch, --prerelease

ex: changelogen --bump --premajor or changelogen --bump --premajor=alpha

[codecov]

Codecov Report

Merging #70 (88e0254) into main (fbc32cc) will increase coverage by 0.55%.
The diff coverage is 77.27%.

❗ Current head 88e0254 differs from pull request most recent head 2a4516f. Consider uploading reports for the commit 2a4516f to get more accurate results

@@            Coverage Diff             @@
##             main      #70      +/-   ##
==========================================
+ Coverage   70.65%   71.21%   +0.55%     
==========================================
  Files           7        7              
  Lines         777      792      +15     
  Branches       90       90              
==========================================
+ Hits          549      564      +15     
  Misses        228      228              

Impacted Files	Coverage Δ
src/semver.ts	30.95% <77.27%> (+15.01%)	⬆️

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[pi0]

Thanks for the pull-request dear @aa900031 ❤️ I have pushed few refactors to simplify the implementation before merge.