Update CI configuration.

.github/workflows/ci.yml

@@ -1,15 +1,17 @@
 name: build
 on:
   push:
+    branches: [main]
   pull_request:
+    branches: [main]
   schedule:
     - cron: '20 16 * * 0'
 jobs:
   build:
     runs-on: ubuntu-latest
     steps:
       - name: Download source
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: Crystal Ameba Linter
         uses: crystal-ameba/[email protected]
         env:
@@ -21,4 +23,4 @@ jobs:
       - name: Install shards
         run: shards install
       - name: Run tests
-        run: crystal spec
+        run: crystal spec -v