[RRFC] Publish on JSR

JSR is a TS-first ESM registry: https://jsr.io/#why-jsr

This would be better than NPM for browser projects, but Lit is more likely to be used in the browser than a Node JS project.

Lit is also TS-first with ES module imports. 

Should Lit (all modules) be published on JSR, as well as NPM?