feat: add GH workflow to build image

.github/workflows/relay.yml

@@ -0,0 +1,93 @@
+#Tabs not spaces, you moron :)
+
+name: CI for netris:relay
+
+on:
+    pull_request:
+        paths:
+            - "relay.Dockerfile"
+            - ".github/workflows/relay.yml"
+    schedule:
+        - cron: 0 0 * * * # At the end of everyday
+    push:
+        branches: [main]
+        paths:
+            - "relay.Dockerfile"
+            - ".github/workflows/relay.yml"
+        tags:
+            - v*.*.*
+    release:
+        types: [created]
+
+concurrency:
+    group: ${{ github.workflow }}-${{ github.ref == 'refs/heads/main' && github.run_id || github.event.pull_request.number || github.ref }}
+    cancel-in-progress: true
+
+env:
+    REGISTRY: ghcr.io
+    IMAGE_NAME: wanjohiryan/netris
+    BASE_TAG_PREFIX: relay
+
+jobs:
+    build-docker-pr:
+        name: Build image on pr
+        runs-on: ubuntu-latest
+        if: ${{ github.event_name == 'pull_request' }}
+        steps:
+            -
+              name: Checkout repo
+              uses: actions/checkout@v4
+            - 
+              name: Setup Docker Buildx
+              uses: docker/setup-buildx-action@v3
+            - 
+              name: Build Docker image
+              uses: docker/build-push-action@v5
+              with:
+                file: relay.Dockerfile
+                context: ./
+                push: false
+                load: true
+                tags: netris:relay
+
+    build-docker-main:
+        name: Build image on merge
+        if: ${{github.ref == 'refs/heads/main'}}
+        runs-on: ubuntu-latest
+        permissions:
+            contents: read
+            packages: write
+        steps:
+            -
+              name: Checkout repo
+              uses: actions/checkout@v4
+            - 
+              name: Log into registry ${{ env.REGISTRY }}
+              uses: docker/login-action@v3
+              with:
+                registry: ${{ env.REGISTRY }}
+                username: ${{ github.actor }}
+                password: ${{ secrets.GITHUB_TOKEN }}
+            - 
+              name: Extract Container metadata
+              id: meta
+              uses: docker/metadata-action@v5
+              with:
+                images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}/${{ env.BASE_TAG_PREFIX }}
+                #
+                #tag on release, and a nightly build for 'dev'
+                tags: |
+                  type=raw,value=nightly,enable={{is_default_branch}}
+                  type=ref,event=tag
+                  type=semver,pattern={{version}}
+                  type=semver,pattern={{major}}.{{minor}}
+                  type=semver,pattern={{major}}
+            - 
+              name: Build Docker image
+              uses: docker/build-push-action@v5
+              with:
+                file: relay.Dockerfile
+                context: ./
+                push: true
+                tags: ${{ steps.meta.outputs.tags }}
+                labels: ${{ steps.meta.outputs.labels }}