New service: JSR

### 📋 Description

https://jsr.io/ is a JS/TS registry from the creators of deno
Announcement: https://deno.com/blog/jsr_open_beta

### 🔗 Data

https://jsr.io/docs/api

Interestingly, JSR has two APIs we could use

There's what I'm going to call a "native" API
https://jsr.io/docs/api#jsr-registry-api

but then there is the "npm compatibility registry API"
https://jsr.io/docs/api#npm-compatibility-registry-api

The interesting thing about this is it serves up JSR data in the same response format as NPM's API so in theory we should be able to re-use the code for our suite of NPM badges to also cover JSR quite easily.

Unfortunately, although the response format is supposed to be the same, the URL schema isn't so you can't just plug in `?registry_uri=https%3A%2F%2Fnpm.jsr.io` to our existing NPM badges and have them work out of the box.

### 🎤 Motivation

I don't especially want to use this myself but I figure its useful to have a tracking issue for it.

Start by reading the JSR API documentation and reviewing the existing NPM badge implementations. Compare the native and npm-compatibility APIs, then define which badges and URL mappings are in scope; the work is done when the selected JSR badges return correct output through their supported URLs.

Written by the indexing model from the issue text.