Add JSDoc ESLint script

[ntwb]

Description

This PR replaces #4506 due to unresolvable merge conflicts

How has this been tested?

Running npm run lint:jsdoc in a terminal.

Notes:

• This script is separate from the default ESLint task as including causes too many errors and noise when run
• The script does not run at all in any Travis CI job
• The configuration has been added as a standalone dedicated JSDoc configuration in the eslint/ folder, although this is a temporary folder for ESLint configuration it wil suffice for the time being.
• A WordPeess Core ticket #WP43828 has also been created to add the same script to core which will add the ongoing ''JavaScript Inline Docs Initiative''

Screenshots

Types of changes

JSDoc ESLint code linting

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.

[aduth]

Like in #4245, could we consider integrating eslines to mark changed lines as offending errors?

These rules will not be respected if they're not enforced.

[aduth]

What needs to happen to revive this pull request? Or should we close and start anew?

[aduth]

Closing as stale without response.

[aduth]

I'd still like to see this at some point. I opened #15193 as a task issue after trying (and failing) to implement it again in the current codebase.