chore: auto-publish docker images (#1373)

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## Changes

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.dockerignore

@@ -6,6 +6,7 @@
 !sdks/full/rust/src
 !packages
 !resources/legacy/proto
+!externals/
 
 sdks/runtime
 svc/**/*.md

.github/actions/docker-setup/action.yaml

@@ -0,0 +1,32 @@
+name: 'Docker Setup'
+description: 'Set up Docker Buildx and log in to Docker Hub'
+inputs:
+  docker_username:
+    description: 'Docker Hub username'
+    required: true
+  docker_password:
+    description: 'Docker Hub password'
+    required: true
+  github_token:
+    description: 'GitHub token'
+    required: true
+runs:
+  using: 'composite'
+  steps:
+    - name: Set up Docker Buildx
+      uses: docker/setup-buildx-action@v3
+
+    - name: Log in to Docker Hub
+      uses: docker/login-action@v3
+      with:
+        username: ${{ inputs.docker_username }}
+        password: ${{ inputs.docker_password }}
+
+    # This will be used as a secret to authenticate with Git repo pulls
+    - name: Create .netrc file
+      run: |
+        echo "machine github.com" > ${{ runner.temp }}/netrc
+        echo "login x-access-token" >> ${{ runner.temp }}/netrc
+        echo "password ${{ inputs.github_token }}" >> ${{ runner.temp }}/netrc
+      shell: bash
+