create dummy cpp build job

.gitea/workflows/demo.yaml

@@ -4,17 +4,35 @@ run-name: ${{ gitea.actor }} is testing out Gitea Actions 🚀
 on: [push]
 
 jobs:
-  Explore-Gitea-Actions:
+  build:
     runs-on: debian12
+    container:
+      image: cpp-builder-a
     steps:
-      - run: echo "🎉 The job was automatically triggered by a ${{ gitea.event_name }} event."
-      - run: echo "🐧 This job is now running on a ${{ runner.os }} server hosted by Gitea!"
-      - run: echo "🔎 The name of your branch is ${{ gitea.ref }} and your repository is ${{ gitea.repository }}."
-      - name: Check out repository code
-        uses: actions/checkout@v4
-      - run: echo "💡 The ${{ gitea.repository }} repository has been cloned to the runner."
-      - run: echo "🖥️ The workflow is now ready to test your code on the runner."
-      - name: List files in the repository
+      - name: clone
+        uses: actions/checkout@v3
+
+      - name: build
         run: |
-          ls ${{ gitea.workspace }}
-      - run: echo "🍏 This job's status is ${{ job.status }}."
+          g++ -o app main.cpp
+
+      - name: upload
+        uses: actions/upload-artifact@v3
+        with:
+          name: build-artifact
+          path: app
+
+  execute:
+    runs-on: debian12
+    container:
+      image: cpp-builder-a
+    steps:
+      - name: download
+        uses: actions/download-artifact@v3
+        with:
+          name: build-artifact
+
+      - name: execute
+        run: |
+          chmod +x app
+          ./app