Update base image to ghcr.io image.

Author: markstory

docs.Dockerfile

@@ -1,5 +1,5 @@
 # Generate the HTML output.
-FROM markstory/cakephp-docs-builder as builder
+FROM ghcr.io/cakephp/docs-builder as builder
 
 RUN pip install git+https://github.com/sphinx-contrib/video.git@master
 
@@ -15,7 +15,7 @@ RUN cd /data/docs-builder \
   && cp /data/docs/static/* /data/website/html/_static/
 
 # Build a small nginx container with just the static site in it.
-FROM markstory/cakephp-docs-builder:runtime as runtime
+FROM ghcr.io/cakephp/docs-builder:runtime as runtime
 
 # Configure search index script
 ENV LANGS="en fr ja pt"