refactor: fs.rmdir -> fs.rm

[erickzhao]

(node:23706) [DEP0147] DeprecationWarning: In future versions of Node.js, fs.rmdir(path, { recursive: true }) will be removed. Use fs.rm(path, { recursive: true }) instead
(Use `node --trace-deprecation ...` to show where the warning was created)

Node 16: https://nodejs.org/api/deprecations.html#DEP0147

[codecov]

Codecov Report

Merging #133 (d9354ee) into main (29e44a6) will not change coverage.
The diff coverage is 100.00%.

❗ Current head d9354ee differs from pull request most recent head 3f0503b. Consider uploading reports for the commit 3f0503b to get more accurate results

@@           Coverage Diff           @@
##             main     #133   +/-   ##
=======================================
  Coverage   75.43%   75.43%           
=======================================
  Files           1        1           
  Lines          57       57           
=======================================
  Hits           43       43           
  Misses         14       14           

Impacted Files	Coverage Δ
src/index.js	75.43% <100.00%> (ø)

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[malept]

1. Why didn't CI run for this PR? 😕
2. fs.rm doesn't exist until Node 14, I think?

[eXhumer]

I came across a deprecation warning (node:88445) [DEP0147] DeprecationWarning: In future versions of Node.js, fs.rmdir(path, { recursive: true }) will be removed. Use fs.rm(path, { recursive: true }) instead while trying to build darwin DMGs for my Electron app.

fsPromises.rm was added since 14.14.0 update. A check for the runtime node version using process.versions.node can be used to select the correct method

      const nodeVersion = process.versions.node.split('.').map(segment => parseInt(segment));
      await (nodeVersion[0] > 14 || (nodeVersion[0] === 14 && nodeVersion[1] >= 14) ?
        fs.rm :
        fs.rmdir)(specDir, { recursive: true, maxRetries: 2 });

NOTE: fsPromises.rmdir was added in v10.0.0, recursive was added since v12.10.0

[erickzhao]

Will merge this after #178