Add ability to use via custom hook

[shawnmcknight]

Description 📝

This PR adds a custom hook useScrollbarSize to the exports from the package. The existing component syntax was retained for backwards compatibility, but will be deprecated in a future major release (likely 4.0).

Conceptually, the hook works identically to the component in that it will measure the scrollbar sizes and react to changes which might affect the size of the scrollbar (e.g. change to browser zoom factor). This is intended merely as a usability enhancement as use of the hook is significantly easier than use of the component.

All examples and guides have been updated to favor using the hook instead of the component

Type of change 💎

• New feature (non-breaking change which adds functionality)

Example code 📜

See changes to README.md for updated examples.

How Has This Been Tested? 🚦

• Unit tests were created and updated as needed.
• Both examples (hook and component) were run to ensure everything works as intended.
• Consumed the library from another project to ensure that it runs properly

Checklist 🏁

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• New and existing unit tests pass locally with my changes
• My changes pass lint, prettier, and TS checks
• I have added tests that prove my fix is effective or that my feature works
• I have commented my code, particularly in hard-to-understand areas

[shawnmcknight]

@kgregory I would appreciate it if you could give this one a review.

[shawnmcknight]

@Noitidart tagging you since you had asked about this feature.

[Noitidart]

Thank you. @shawnmcknight - checking now!

[Noitidart]

Left some nits :) Thanks for this amazing work!

[kgregory]

Looks good!

I like @Noitidart's suggestion for local state. I also think it may be best to heed the React warning about referencing a ref's value in the useEffect cleanup.

[kgregory]

Looks good, found a typo that I missed in the initial review, but I'm approving.

[shawnmcknight]

Thanks for the review @kgregory and @Noitidart !