Add links to further information on MDN

[dmeiz]

Hi, this summary is great! It's a great balance of concise and thorough.

Sometimes I do want more details and end up on a relevant MDN page. What do you think about adding links to further information on MDN?

I can put together a PR if that sounds useful.

Thx, Dan

[abierbaum]

I don't know about anyone else, but this sounds very useful to me.

[stephenhuh]

Definitely agree. Would like to see relevant MDN pages.