Add dotnet console app. Remove c file.

.gitea/workflows/ci.yml

@@ -6,10 +6,8 @@ jobs:
         runs-on: ubuntu-latest
         steps:
             - uses: actions/checkout@v4
-            - name: build using gcc
-              run: gcc -Wall -Werror main.c -o program
-            - name: Archive production artifacts
-              uses: actions/upload-artifact@v3
+            - uses: actions/setup-dotnet@v3
               with:
-                  name: program
-                  path: program
+                  dotnet-version: "8.0.x"
+            - run: dotnet restore
+            - run: dotnet build