Should this be an RFC?

• This is not a substantial change

Which package is this a feature request for?

Lit Core (lit / lit-html / lit-element / reactive-element)

Description

MathML has very good browser support now: https://developer.mozilla.org/en-US/docs/Web/MathML#browser_compatibility

We should support MathML fragments with a new math template tag like we do with SVG and the svg tag.

Alternatives and Workarounds

None. Without parsing fragments inside a <math> tag, elements will not be parsed into the correct namespace.