Add screenshot(s) to `README.md` showing usage

[with-heart]

I discovered this extension today and was able to figure out how it works, but screenshots would make that much more obvious.

[Anita-ihuman]

I will like to take on this issue

[kaicataldo]

@Anita-ihuman That would be great, thanks!

[Anita-ihuman]

I want to be clear on something
Am I go ahead and include all the fixes in the REadme? Or we are using wiki pages

[nickserv]

I think we should be fine with just a README.md and CONTRIBUTING.md (eventally), unless you have suggestions for other wiki pages.

[Anita-ihuman]

Please review my PR@nickmccurdy