Enable "merge_group" events for GitHub's merge queue

We need to also trigger on the "merge_group" event for GitHub's
merge queue to work. This is the same as <freedomofpress/securedrop-dev-docs#130>.

.github/workflows/build.yml

@@ -1,5 +1,5 @@
 name: Package builds
-on: [push, pull_request]
+on: [merge_group, push, pull_request]
 
 defaults:
   run:
@@ -36,7 +36,7 @@ jobs:
           PKG_DIR=../proxy make -C securedrop-builder requirements
           git config --global --add safe.directory "$GITHUB_WORKSPACE"
           git diff --ignore-matching-lines=# --exit-code
-          
+
 
   build-debs:
     strategy:

.github/workflows/cargo-vet.yml

@@ -2,7 +2,7 @@
 
 name: cargo vet
 
-on: [push, pull_request]
+on: [merge_group, push, pull_request]
 
 jobs:
   cargo-vet:

.github/workflows/ci.yml

@@ -1,5 +1,5 @@
 name: CI
-on: [push, pull_request]
+on: [merge_group, push, pull_request]
 
 defaults:
   run:

.github/workflows/sdk.yml

@@ -1,5 +1,5 @@
 name: SDK
-on: [push, pull_request]
+on: [merge_group, push, pull_request]
 
 defaults:
   run:

.github/workflows/test.yml

@@ -1,5 +1,5 @@
 name: Tests
-on: [push, pull_request]
+on: [merge_group, push, pull_request]
 
 defaults:
   run: