Enable the zstd decoder (#36530)

Uses the `zstd` support from `async-compression` to support zstd
Content-Encoding.

Testing: Covered by wpt tests.

Signed-off-by: webbeef <me@webbeef.org>

components/net/http_loader.rs

@@ -184,7 +184,7 @@ fn set_default_accept_encoding(headers: &mut HeaderMap) {
     // TODO(eijebong): Change this once typed headers are done
     headers.insert(
         header::ACCEPT_ENCODING,
-        HeaderValue::from_static("gzip, deflate, br"),
+        HeaderValue::from_static("gzip, deflate, br, zstd"),
     );
 }