Added markdown linting

[dpwatrous]

Also fixed up all markdown files so there are no linting errors. Uses https://github.com/DavidAnson/markdownlint

[gingi]

Love it.

[dpwatrous]

Looks like we had some ES6 polyfills for unit tests that relied on a transitive dependency. If the CI tests pass without them then I think we can safely say they're not needed.

[codecov]

Codecov Report

Merging #2292 (597db9a) into master (f8b4ab8) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2292   +/-   ##
=======================================
  Coverage   65.19%   65.19%           
=======================================
  Files         903      903           
  Lines       25712    25712           
  Branches     5105     5105           
=======================================
  Hits        16763    16763           
  Misses       8949     8949           

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[dpwatrous]

One more thing to point out on this PR: I found some references to private NPM repos in package-lock.json and just regenerated it. I did it with NPM 7, so this does upgrade package-lock to v2.

We've already switched the package-lock files for the portal so IMO we might as well do it for Batch Explorer.