new egg: cmark

[Harley Swick]

Hi there!

I'm announcing the first release of cmark and would like to add it to the coop.

cmark is a wrapper for the commonmark C library. It also includes a cmark->sxml 
function
that I have specifically implemented to be a drop-in replacement for lowdown.

There is a different cmark egg for Chicken 4. Since my additions are 
significantly larger than
the total of the old egg, I didn't feel it was fair to drop a bunch of strange 
code on someone
who may not want to be stuck maintaining it. I have added aliases to make this 
egg
a compatible replacement for users upgrading from 4 to 5. I don't foresee any 
issues with conflicts since
this egg only works with Chicken 5.

The wiki page has been made already.

Thanks!

Wiki:
http://wiki.call-cc.org/eggref/5/cmark
Source:
https://git.sr.ht/~fancycade/chicken-cmark