Added a section explaining how to build a docker image from source code

Getting-Started.md

@@ -135,6 +135,21 @@ mv Dockerfile.go_build Dockerfile
 docker build --no-cache -t 'chrislusf/seaweedfs' .
 ```
 
+### Building image from source code
+Create an executable for docker and move it to the docker folder
+```bash
+cd weed
+make build_docker
+mv weed ../docker/
+cd ..
+```
+
+Build the image
+```bash
+cd docker
+docker build -f Dockerfile.local --no-cache -t localregistry/seaweedfs
+```
+
 ### In production
 
 You can use docker volumes to persist data: