Allow references and notes in fenced divs

[Witiko]

Our implementation of fenced divs does not allow for reference definitions. This is because our implementation uses the parsers.blankline pattern instead of the Blank rule, which includes blank lines and references, among other things.

This pull request is a port of Witiko#307.

[Witiko]

@Omikhleia a review would be appreciated. I suppose you may want this in SILE as well.

[Omikhleia]

a review would be appreciated. I suppose you may want this in SILE as well.

Good catch...
It also seems to fix footnotes in fenced divs (with the notes=true extension)

::: {.cit custom-style=raggedleft}
I am a _fenced_ div with a note[^1]

[^1]: My note

:::

Before, such notes were not parsed and rendered, with the proposed change it seems to me they also work now.
(N.B. The blank line after the footnote content is needed, but it seems to be the case too with Pandoc.)

Maybe it could be added to the non-regression tests too, to ensure it stays covered?

EDIT:

but it seems to be the case too with Pandoc.

Confirmed at least with Pandoc 2.18.

[Witiko]

Maybe it could be added to the non-regression tests too, to ensure it stays covered?

Good thinking, I added a test for notes in fenced divs. Thank you for the review.