ci: Add docker-pr.yml workflow.

Author: jnms-me

.github/workflows/docker-pr.yml

@@ -0,0 +1,31 @@
+name: "docker: Build and push ghcr.io/zeuswpi/tap:pr-[number]"
+
+on:
+  pull_request:
+
+concurrency:
+  group: docker-nightly-${{ github.ref_name }}
+  cancel-in-progress: true
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: docker/setup-buildx-action@v3
+
+      - uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ github.token }}
+
+      - uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: Dockerfile.production
+          push: true
+          tags: |
+            ghcr.io/zeuswpi/tap:pr-${{ github.event.pull_request.number }}
+            ghcr.io/zeuswpi/tap:pr-${{ github.event.pull_request.number }}-${{ github.sha }}