new egg: matchertext

matchertext is a "syntactic discipline" that allows for cross-language embe=
dding
of source code. It was invented by Bryan Ford (who also invented parsing
expression grammars and packrat parsing).

The matchertext egg extends the Scheme language to be able to host matchert=
ext
in string literals.

- release-info: https://git.sr.ht/~nagbu/matchertext/blob/main/matchertext.=
release-info
- docs: https://wiki.call-cc.org/eggref/5/matchertext

Thanks for adding it to the coop.

Cheers,
Hern=C3=A1n