chore(build): Use base Docker images on the Github registry

DockerHub has started rate-limiting which is failing builds.
The base build/runtime images are now published to the Github org.

Dockerfile.release

@@ -2,7 +2,7 @@
 # Builder image
 # ------------------------------------------------
 
-FROM thumbsupgallery/build:alpine as build
+FROM ghcr.io/thumbsup/build:node-10
 
 # Install thumbsup locally
 WORKDIR /thumbsup
@@ -18,7 +18,7 @@ RUN npm install thumbsup@${PACKAGE_VERSION}
 # Runtime image
 # ------------------------------------------------
 
-FROM thumbsupgallery/runtime:alpine
+FROM ghcr.io/thumbsup/runtime:node-10
 
 # Use tini as an init process
 # to ensure all child processes (ffmpeg...) are always terminated properly

Dockerfile.test

@@ -1,5 +1,5 @@
 # Node.js + build dependencies + runtime dependencies
-FROM thumbsupgallery/build:alpine
+FROM ghcr.io/thumbsup/build:node-10
 
 # Switch to a non-root user
 # So we can test edge-cases around file permissions