This PR extends the extension API with some additional features to
support auto-updating extensions:
- The `GET /extensions` endpoint now accepts an optional `ids` parameter
that can be used to filter the results down to just the extensions with
the specified IDs.
- This should be a comma-delimited list of extension IDs (e.g.,
`wgsl,gleam,tokyo-night`).
- A new `GET /extensions/:extension_id` endpoint that returns all of the
extension versions for a particular extension.
Extracted from #9890, as these changes can be landed and deployed
independently.
Release Notes:
- N/A
Co-authored-by: Max <max@zed.dev>