I have just uploaded version 0.21 -- officially it's still beta, but it should be complete and stable enough for practical use now.
This is a minimalist design, so close to plain text that I do not even call it a markup language. Still, I have been writing software for 40 years, have edited and typeset texts for 20 years, and have been a publisher for more than 10 years now, so, some thought and experience has gone into this.
Anyway, feel free to use, comment, criticize, improve, or ignore!