Update: Adding missing documentation features for useWindowSize hook

[francoisdillinger]

Pull Request Description

Description Added UseWindowSizeDemo.jsx and useWindowSize.mdx files for documentation details.

Acceptance Criteria

• [x] The documentation for a hook/utility should show, as best as possible, how it works in action, so a complete usage example
• [x] The newly added item should be referenced in all other instances where other items are referenced in the docs/readme.

Note useWindowSize is referenced in docs/readme but not in root/readme.

Demo:

[DavidHDev]

Looks good, will merge after the next package release! 👍🏻