* HTML reader: Handle cite attribute for quotes. If a `<q>` tag has a `cite` attribute, we interpret it as a Quoted element with an inner Span. Closes#5798
* Refactor url canonicalization into a helper function
* Modify HTML writer to handle quote with cite.
[0]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/q
* XML.toEntities: changed type to Text -> Text.
* Shared.tabFilter -- fixed so it strips out CRs as before.
* Modified writers to take Text.
* Updated tests, benchmarks, trypandoc.
[API change]
Closes#3731.
