fix: Skip escaping if already escaped in the code tag.

[shibomb]

Resolves #587

This is a proposal.
It seems to work well on the following page in my local env.
/reference/p5/createInput/
/reference/p5/Boolean/
/reference/p5/Number/

changes:

Check if the content is already escaped by looking for common HTML entities in code tag.
If already escaped, skip escaping.

[davepagurek]

This is a good fix for right now while we have stuff written in an inconsistent format. We should also address that at the source (details in #587 (comment)) but this will help us not have broken content in the mean time!

[davepagurek]

One note is that it means we can't easily write code in p5 explaining how HTML escaping works because if we try to explicitly write < as I've done here, it would render as < in our docs. I think that's fine since we probably don't need to do that in p5, but once the source is addressed, the plan will be to remove this check again.