Require successful formatting in the CI pipeline

Author: abelbraaksma

.github/workflows/build.yaml

@@ -3,6 +3,25 @@ name: ci-build
 on: [pull_request]
 
 jobs:
+  verify_formatting:
+    runs-on: ubuntu-latest
+    name: Verify code formatting
+
+    steps:
+      - name: checkout-code
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - name: setup-dotnet
+        uses: actions/setup-dotnet@v3
+  
+      - name: tool restore
+        run: dotnet tool restore
+  
+      - name: validate formatting
+        run: dotnet fantomas . --check
+
   build:
     name: Build
     runs-on: windows-latest
@@ -12,9 +31,11 @@ jobs:
         uses: actions/checkout@v3
         with:
           fetch-depth: 0
+
       # setup dotnet based on global.json
       - name: setup-dotnet
         uses: actions/setup-dotnet@v3
+
       # build it, test it, pack it
       - name: Run dotnet build (release)
         # see issue #105