## Summary
This PR adds a [Workers
KV](https://developers.cloudflare.com/workers/runtime-apis/kv/)-based
database to the playground, which enables us to associate shared
snippets with a stable ID, which in turn allows us to generate short
URLs, rather than our existing extremely-long URLs.
For now, the URLs are based on UUID, so they look like
https://play.ruff.rs/a1c40d58-f643-4a3e-bc23-15021e16acef. (This URL
isn't expected to work, as the playground isn't deployed; it's only
included as an example.)
There are no visible changes in the UI here -- you still click the
"Share" button, which copies the link to your URL. There's no
user-visible latency either -- KV is very fast.
For context, with Workers KV, we provision a Workers KV store in our
Cloudflare account (`wrangler kv:namespace create "PLAYGROUND"`), and
then create a Cloudflare Worker that's bound to the KV store via the
`wrangler.toml`:
```toml
name = "db"
main = "src/index.ts"
compatibility_date = "2023-08-07"
kv_namespaces = [
{ binding = "PLAYGROUND", id = "672e16c4fb5e4887845973bf0e9f6021", preview_id = "0a96477e116540e5a6e1eab6d6e7523e" }
]
```
The KV store exists in perpetuity, while the Worker can be updated,
deployed, removed, etc. independently of the KV store. The Worker itself
has unfettered access to the KV store. The Worker is exposed publicly,
and just does some basic verification against the request host.
