Drop use of rimraf

[binyamin]

Fixes #103

I replaced rimraf with the native Node.js fs.rm() function. This requires Node.js 14, which is the lowest LTS version anyway. I updated the CI environments to match.

[codecov[bot]]

Codecov Report

Merging #110 (b8f15dc) into master (8b6c4cb) will decrease coverage by 0.35%. The diff coverage is 100.00%.

:exclamation: Current head b8f15dc differs from pull request most recent head 05eea65. Consider uploading reports for the commit 05eea65 to get more accurate results

@@            Coverage Diff             @@
##           master     #110      +/-   ##
==========================================
- Coverage   95.70%   95.34%   -0.36%     
==========================================
  Files          25       25              
  Lines        1419     1417       -2     
  Branches      277      277              
==========================================
- Hits         1358     1351       -7     
- Misses         61       66       +5     

Impacted Files	Coverage Δ
lib/remove.js	100.00% <100.00%> (ø)
lib/utils/tree_walker.js	82.17% <0.00%> (-3.88%)	:arrow_down:

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[szwacz]

Thank you. Will check it soon :)

[szwacz]

Released in v5.0.0 (finally :D )