add demo workflow

.gitea/workflows/build-and-test.yaml

@@ -0,0 +1,18 @@
+name: Build & Test
+run-name: Build & Test
+on: [push]
+
+jobs:
+  build-and-test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository code
+        uses: actions/checkout@v4
+      - name: Install rust
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+      - name: Build
+        run: cargo build
+      - name: Test
+        run: cargo test