Add docker image README.md

docker/README.md

+Development Docker Image
+========
+
+* Login in Xiaomi Docker Hub
+```
+docker login docker.d.xiaomi.net
+```
+* Build the image
+```
+docker build -t docker.d.xiaomi.net/mace/mace-dev .
+```
+
+* Push the image to Xiaomi Docker Hub
+```
+docker push docker.d.xiaomi.net/mace/mace-dev
+```
+
+* Pull and run the image
+```
+# Set 'host' network to use ADB
+docker run -it --net=host docker.d.xiaomi.net/mace/mace-dev /bin/bash
+```