Add support for merge queue (#273)

Author: lfrancke

.github/pull_request_template.md

@@ -10,5 +10,3 @@
 - [ ] Documentation added (or not applicable)
 - [ ] Changelog updated (or not applicable)
 - [ ] Cargo.toml only contains references to git tags (not specific commits or branches)
-
-Once the review is done, comment `bors r+` (or `bors merge`) to merge. [Further information](https://bors.tech/documentation/getting-started/#reviewing-pull-requests)

.github/workflows/build.yml

@@ -11,6 +11,7 @@ on:
     tags:
       - "*"
   pull_request:
+  merge_group:
 
 env:
   CARGO_TERM_COLOR: always