Add IBM Plex Math

**Font Project Git Repo URL:**

https://github.com/IBM/plex/tree/master/packages/plex-math

**Super short description of the Font Family:**

From https://github.com/IBM/plex:

> Additionally, we have introduced IBM Plex® Math. This highly anticipated release includes over 5,000 new glyphs, covering a wide range of mathematical symbols such as alphanumeric, double-struck, Fraktur, operators, script, icons, arrows, Greek letters, phonetics, technical and geometric shapes — making it one of the most complete math fonts available today. IBM Plex Math provides a fresh and comprehensive alternative to STIX and Microsoft’s Cambria. Its compatibility with IBM Plex Serif Regular makes it an ideal choice for IBM researchers and mathematicians.

**Requirements:**

It is a companion to IBM Plex Serif that is already on Google Fonts.