Add script to build Docker image from forked code

README-fork.md

@@ -4,3 +4,17 @@ This is my personal fork of `Athou/commafeed` with some tweaks:
 
 - "Infrequent" tab - like "All" but limits to blogs w/ an average post interval greater than a user-configurable number of days
 - User preference to disable the swipe-to-open-menu gesture on mobile
+
+## Building
+
+Use `gmfork-build-docker.sh` to build the JVM Docker image for `linux/amd64`:
+
+```sh
+DOCKER_REGISTRY=myregistry.example.com ./gmfork-build-docker.sh
+```
+
+To run locally:
+
+```sh
+docker run -p 8082:8082 $DOCKER_REGISTRY/commafeed-fork:latest
+```