tools: update Markdown linter to be cross-platform

Prior to this commit, the dependencies were not
matching the build procedure. This has been
corrected and it has the added benefit of being
able to be built on Windows as well.

* continue using `rollup` rather than `ncc`
* do not require `fs-event`s for non-macOS
* use `npx` and `shx` for cross-platform building
* ensure `lint-md-rollup` runs before `lint-md`

PR-URL: #31239
Reviewed-By: Rich Trott <rtrott@gmail.com>