chore(ui): Copy some attributes from matrix-sdk

The others should likely be copied at some point as well, but including
the readme as crate documentation is not currently useful since the
readme for the ui crate is empty, and warning about missing docs or
debug implementations would make CI fail without substantial extra work.

crates/matrix-sdk-ui/src/lib.rs

@@ -12,6 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#![cfg_attr(target_arch = "wasm32", allow(clippy::arc_with_non_send_sync))]
+#![cfg_attr(docsrs, feature(doc_auto_cfg))]
+
 use ruma::html::HtmlSanitizerMode;
 
 mod events;