feat (msc3266): Room Summary API

Cargo.toml

@@ -172,6 +172,8 @@ features = [
   "ring-compat",
   "state-res",
   "unstable-msc2448",
+  #[cfg(feature = "msc3266")]
+  "unstable-msc3266",
   "unstable-msc4186",
 ]
 git = "https://github.com/ruma/ruma.git"
@@ -189,10 +191,11 @@ nix = { version = "0.30", features = ["resource"] }
 backend_rocksdb = ["rocksdb"]
 backend_sqlite = ["sqlite"]
 conduit_bin = ["axum"]
-default = ["backend_rocksdb", "backend_sqlite", "conduit_bin", "systemd"]
+default = ["backend_rocksdb", "backend_sqlite", "conduit_bin", "proposal_msc3266", "systemd"]
 jemalloc = ["tikv-jemallocator"]
 sqlite = ["parking_lot", "rusqlite", "tokio/signal"]
 systemd = ["sd-notify"]
+proposal_msc3266 = ["msc3266"]
 
 [[bin]]
 name = "conduit"