Build/Test Tools: Enable JSDocs to be linted with ESLint.
As part of the [Javascript Inline Docs Initiative](https://make.wordpress.org/core/handbook/docs/inline/js/) this add some tooling to lint Javascript docblocks. Two new commands:
npm run lint:jsdoc
npm run lint:jsdoc:fix
The latter will run the linter and try to fix an possible issues automatically.
Fixes #43828. Props netweb, atimmer, kamataryo, whyisjake.