Add to README steps for pushing images.

Author: carlosperate

README.md

@@ -27,3 +27,17 @@ docker run --name ubit-toolchain-container -it --entrypoint /bin/bash ubit-toolc
 ```
 docker cp ubit-toolchain-container:/home/artefacts .
 ```
+
+### Publish image
+
+```
+docker login ghcr.io -u <your_username>
+docker images
+docker tag IMAGE_ID ghcr.io/OWNER/IMAGE_NAME:VERSION
+docker push ghcr.io/OWNER/IMAGE_NAME:VERSION
+```
+
+```
+docker tag 36ebf8c6ccbf ghcr.io/carlosperate/ubit-toolchain:0.1.0
+docker push ghcr.io/carlosperate/ubit-toolchain:0.1.0
+```