Fix auto detection for path of shellcheck.exe on Windows

[jfcherng]

Issues

• There is no bash/which on Windows, by default.
• Even if using the bash/which from git-bash or WSL, the returned path is Unix-style. And Node.js on Windows is not happy with it.

Solutions

• Use cmd.exe as the default shell on Windows.
• Use the which package to find shellcheck in a cross-platform way.

[codecov]

Codecov Report

Merging #563 (d411668) into main (f1352fc) will decrease coverage by 0.18%.
The diff coverage is 55.55%.

❗ Current head d411668 differs from pull request most recent head ad1e7d0. Consider uploading reports for the commit ad1e7d0 to get more accurate results

@@            Coverage Diff             @@
##             main     #563      +/-   ##
==========================================
- Coverage   74.85%   74.66%   -0.19%     
==========================================
  Files          19       19              
  Lines         676      679       +3     
  Branches      119      121       +2     
==========================================
+ Hits          506      507       +1     
+ Misses        154      153       -1     
- Partials       16       19       +3     

Impacted Files	Coverage Δ
server/src/linter.ts	89.04% <50.00%> (+2.96%)	⬆️
server/src/util/sh.ts	84.21% <57.14%> (-4.26%)	⬇️
server/src/analyser.ts	84.00% <0.00%> (-0.98%)	⬇️
server/src/server.ts	58.76% <0.00%> (-0.62%)	⬇️
server/src/util/platform.ts	100.00% <0.00%> (+100.00%)	⬆️

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[skovhus]

Thank you so much for fixing this so fast! This was on my todo list. 👏

[skovhus]

@jfcherng any specific reason for using version 2 of the which library? I see that there is a version 3, but haven't looked if there are any breaking changes (e.g. like only supporting ESM)

[jfcherng]

@jfcherng any specific reason for using version 2 of the which library? I see that there is a version 3, but haven't looked if there are any breaking changes (e.g. like only supporting ESM)

I tried v3 at first. It works fine without any code change but it requires Node v14, so it will failed the test for Node v12 here.