Add Forgejo CI workflows

.forgejo/workflows/build.yml

@@ -0,0 +1,35 @@
+name: Build
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    defaults:
+      run:
+        working-directory: src
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+
+      - name: Set up .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: 8.0.x
+
+      - name: Restore local tools
+        run: dotnet tool restore
+
+      - name: Restore dependencies
+        run: dotnet restore CsMic.sln
+
+      - name: Build
+        run: dotnet build CsMic.sln --no-restore