wip: add image build ci job

.github/workflows/ci.yml

@@ -0,0 +1,33 @@
+name: docker
+on:
+  push:
+    branches: main
+  pull_request:
+
+jobs:
+  docker-buildx:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - uses: actions/checkout@v3
+
+      - name: Build and load
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: Containerfile
+          # test with nonstandard uid and gid
+          build-args: |
+            UID=1234
+            GID=1235
+          load: true
+          tags: l7/nvim:latest
+          # could enable push to gh registry
+          push: false
+          cache-from: type=gha
+          cache-to: type=gha,mode=max