This is definitely still a work in progress!

commonmark wraps text in <emph></emph> tags. If I add `asis` to
them, they disappear... which probably means that I just need to add
the `asis` tag to the text nodes :face_palm:

It's now gibberish!

This is why when you run into odd things during development, to
restart and work with a clean environment, because sometimes you
screw up.

This allows us to include the delimiters for the search

Deer lord, I hope this makes sense six months down the line

I had modified `find_between()` from pegboard:::find_between_tags()
(https://github.com/carpentries/pegboard/blob/378c627b4e08869540aa049b678f9c4a560dff59/R/div.R#L125-L159)

My initial modification to extract all of the descendants was in the
context of block math where I knew that I just needed to add the 'asis'
attribute to the nodes. In the context of inline math, where I needed to
create new nodes, this was not feasible since extracting
descendant-or-self would give me duplicate nodes, which would hinder the
process of creating new nodes and lead to stuttering of the output.

Separating out the search functionality into `find_between()` really
helped me fix those two inconsistencies

Co-authored-by: Maëlle Salmon <maelle.salmon@yahoo.se>

Add not math dollar in example

 - add xml_ns_strip() before node insertion events to avoid duplicate
   namespaces from accumulating (see
   https://community.rstudio.com/t/adding-nodes-in-xml2-how-to-avoid-duplicate-default-namespaces/84870)
 - export md_ns() and protect_math() for users of to_xml()
 - protect_tickbox() is now default in to_xml()
 - updated README
 - updated asis tests