fixing runner

.forgejo/workflows/shellcheck.yml

@@ -1,11 +1,18 @@
-name: ShellCheck
+name: CI
 
-on: [push, pull_request]
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
 
 jobs:
   shellcheck:
     runs-on: ubuntu-latest
+    container: ghcr.io/catthehacker/ubuntu:act-22.04
     steps:
-      - uses: https://code.forgejo.org/actions/checkout@v4
+      - uses: actions/checkout@v4
+      - name: Install ShellCheck
+        run: apt-get update && apt-get install -y shellcheck
       - name: Run ShellCheck
         run: shellcheck dotgit.sh demo/demo-note.sh