First cut at CI workflows (#6)

Co-authored-by: Shrukan <shrukan@shrukanslab.xyz>
Reviewed-on: sl-devs/CppTemplate#6

.gitea/workflows/build_image.yml

@@ -0,0 +1,36 @@
+name: Build Image
+run-name: ${{ gitea.ref }} Build
+on:
+  push:
+
+jobs:
+  build-dev-image:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository code
+        uses: actions/checkout@v3
+
+      - name: Install Docker
+        run: curl -fsSL https://get.docker.com | sh
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
+      - name: Log into Gitea
+        uses: docker/login-action@v1
+        with:
+          registry: gitea.shrukanslab.xyz
+          username: ${{ secrets.ROBOT_USERNAME }}
+          password: ${{ secrets.ROBOT_PASSWORD }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v4
+        with:
+          context: .
+          platforms: linux/amd64
+          push: true
+          tags: |
+            gitea.shrukanslab.xyz/CppTemplate/dev-environment:latest
+
+      - name: Logout from Docker Registry
+        run: docker logout gitea.shrukanslab.xyz