ci: Add merge queue trigger to danger workflow (#58467)

Release Notes:

- N/A

.github/workflows/danger.yml

@@ -2,6 +2,7 @@
 # Rebuild with `cargo xtask workflows`.
 name: danger
 on:
+  merge_group: {}
   pull_request:
     types:
     - opened

tooling/xtask/src/tasks/workflows/danger.rs

@@ -9,14 +9,14 @@ pub fn danger() -> Workflow {
     let danger = danger_job();
 
     named::workflow()
-        .on(
-            Event::default().pull_request(PullRequest::default().add_branch("main").types([
+        .on(Event::default()
+            .pull_request(PullRequest::default().add_branch("main").types([
                 PullRequestType::Opened,
                 PullRequestType::Synchronize,
                 PullRequestType::Reopened,
                 PullRequestType::Edited,
-            ])),
-        )
+            ]))
+            .merge_group(MergeGroup::default()))
         .add_job(danger.name, danger.job)
 }