Proposal: Add "Common Errors" page

[developit]

@mcclure brought an interesting idea to light over on this preact issue:

Preact can sometimes produce difficult to understand errors, particularly when not in debug mode. Developers tend to google for these errors, and they often end up on old closed-out issues in the Preact repo, which isn't always helpful and is sometimes misleading.

What if we created a page on the preactjs.com site that listed out common error messages (partial error strings/symbols), and for each included a description of the error and the recommended fix or action to take. The page could be preactjs.com/about/errors, and it wouldn't need to be particularly prominent in the navigation - we'd really be using it to make sure folks googling their error messages end up somewhere truly helpful.