Adds GH workflow to build docker images on version tags

.github/workflows/Dockerfile

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+# GitHub action dockerfile
+# Requires docker experimental features as buildx and BuildKit so not suitable for developers regular use.
+# https://docs.docker.com/develop/develop-images/build_enhancements/#to-enable-buildkit-builds
+
+###########################
+# Build binaries stage
+###########################
+FROM --platform=$BUILDPLATFORM golang:1.16.15-alpine3.15 AS build
+ADD . /app
+WORKDIR /app
+# Arguments required to build binaries targetting the correct OS and CPU architectures
+ARG TARGETOS TARGETARCH
+# Actually building the binaries
+RUN GOOS=$TARGETOS GOARCH=$TARGETARCH go install -v . ./cmd/...
+
+###########################
+# Build docker image stage
+###########################
+FROM alpine:3.15
+COPY --from=build /go/bin /bin
+# 8333  Mainnet Bitcoin peer-to-peer port
+# 8334  Mainet RPC port
+EXPOSE 8333 8334
+ENTRYPOINT ["btcd"]

.github/workflows/dimagespub.yml

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+name: Docker images build and publish
+
+on:
+  push:
+    tags:
+      - v*
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+  # Build for default OS, linux, and common CPU architectures
+  # Reference https://github.com/docker/setup-buildx-action#quick-start
+  TPLATFORMS: linux/amd64,linux/arm64,linux/arm,linux/386
+
+jobs:
+  build-push:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Docker Setup Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@94ab11c41e45d028884a99163086648e898eed25
+
+      - name: Log in to the Container registry
+        uses: docker/login-action@f054a8b539a109f9f41c372932f1ae047eff08c9
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@98669ae865ea3cffbcbaa878cf57c20bbf1c6c38
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+
+      - name: Build and push Docker images
+        uses: docker/build-push-action@ac9327eae2b366085ac7f6a2d02df8aa8ead720a
+        with:
+          file: .github/workflows/Dockerfile
+          labels: ${{ steps.meta.outputs.labels }}
+          platforms: ${{ env.TPLATFORMS }}
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}