Add Checkbot guide and browser extension

[seanw]

Fixes: #

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Short description of what this resolves:

Add link to Checkbot browser extension and Checkbot web speed guide.

Proposed changes:

• Add link to Checkbot browser extension and Checkbot web speed guide.

Disclaimer: I'm the author of the extension and the guide but it seems relevant to your list so I hope you find them helpful.

👍 Thanks for a great resource!

[thedaviddias]

Thanks for the addition @seanw, it seems more appropriate here than on my other project for beginners :)