The HTML writer now supports `EndOfBlock`, `EndOfSection`, and
`EndOfDocument` for reference locations. EPUB and HTML slide
show formats are also affected by this change.
This works similarly to the markdown writer, but with special care
taken to skipping section divs with what regards to the block level.
The change also takes care to not modify the output if `EndOfDocument`
is used.
* 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.
