ci(validation): improve output for readability, use lighter image

.github/workflows/regex.yml

@@ -18,14 +18,10 @@ on:
 jobs:
   validate:
     runs-on: ubuntu-latest
+    container: mcr.microsoft.com/powershell:lts-alpine-3.18
     steps:
       - uses: actions/checkout@v4
 
-      - name: Setup PowerShell
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y powershell
-
       - name: validate
         run: pwsh scripts/validateAllPatterns.ps1