Update the docs for running container images

Author: piki

_planetscale/docs/registry.md

@@ -12,6 +12,22 @@ aws --region us-east-1 ecr list-images --profile build --repository-name 'branch
 ```
 
 If necessary, log into the [`build` profile](https://github.com/planetscale/infra/blob/12ae46f94b7b9ad15b0b1ef00c94d544e590c42f/aws_config#L57-L61) first:
+
 ```
 aws sso login --profile build
 ```
+
+### Run images
+
+To run a MySQL container image locally, first log in if needed:
+
+```
+aws sso login
+aws ecr get-login-password --region us-east-1 | docker login --username AWS --password-stdin 997601596833.dkr.ecr.us-east-1.amazonaws.com
+```
+
+And then run it:
+
+```
+docker run -it 997601596833.dkr.ecr.us-east-1.amazonaws.com/branch/mysql-server:8.0.28-ps-sha4567
+```