List more math fonts on the readme

[xsrvmy]

Using a script to search through a full texlive install, I found the following otf math fonts which are not mentioned in the readme. Perhaps these should be mentioned on the home page:

• Concrete Math
• XCharter Math
• kpfonts-otf (multiple weights and sans support)
• GFS Neohellenic Math
• Erewhon Math
• New Computer Modern (notably has full math coverage like STIX 2)

I wonder if it should also be noted that fonts with math characters but no math able (eg. FreeSerif) do not work. I also wonder if making newcm default at some point will make sense since it has better coverage, and uses ams style mathbb that most people are used to.

[wspr]

Good ideas, thanks! I will have to do more testing before biting the bullet with New-CMMath but if it's better than Latin Modern Math then it sounds like a sensible replacement.