Add note for ghcr releases

Closes: #7

Author: taoky

README.md

@@ -6,16 +6,20 @@ The fast way to use USTC mirrors in your container.
 
 `ustclug/ubuntu`, `ustclug/debian`, `ustclug/fedora`, ~~`ustclug/centos`~~, `ustclug/rocky`, `ustclug/alpine`.
 
+Also published on GHCR: Just prepend `ghcr.io/ustclug/` before the image name.
+
 ## Example
 
 Just add `ustclug/` before the distro official image you are using. For example:
 
-```
-sudo docker run -it --rm debian:11
+```shell
+sudo docker run -it --rm debian:12
 ```
 
 Could be replaced by:
 
-```
-sudo docker run -it --rm ustclug/debian:11
+```shell
+sudo docker run -it --rm ustclug/debian:12
+# or
+sudo docker run -it --rm ghcr.io/ustclug/debian:12
 ```