Move "Other Alternatives Considered" to a separate document

[domenic]

And maybe leave just a paragraph or two summary of each in the main document, linking to the other document for details.

More than half of the document (judging by scrollbar position) is on these alternatives. Although the in-depth analysis is very good to have, it makes the explainer feel a bit unbalanced, and messes up my Ctrl+F process (e.g. half the hits for "anchor" are in the <popup> section, so not actually about the current proposal).

[mfreed7]

Yep, good point. I had left it in for the purposes of the initial discussion, to make "what about this approach instead" type questions easier to answer. But with the recent resolution that the content attribute is a viable way forward, I totally agree. I'll remove the extra sections.

[mfreed7]

This is done.