fix: add dev-mysql57 Docker image link to README

Author: tanhongit

README.md

@@ -16,6 +16,7 @@ In this docker repository, we have built the following images:
 - [cslant/dev-worker83](https://hub.docker.com/r/cslant/dev-worker83)
 - [cslant/dev-php84](https://hub.docker.com/r/cslant/dev-php84)
 - [cslant/dev-worker84](https://hub.docker.com/r/cslant/dev-worker84)
+- [cslant/dev-mysql57](https://hub.docker.com/r/cslant/dev-mysql57)
 - [cslant/dev-mysql](https://hub.docker.com/r/cslant/dev-mysql)
 - [cslant/dev-node22](https://hub.docker.com/r/cslant/dev-node22)
 - [cslant/dev-nginx](https://hub.docker.com/r/cslant/dev-nginx)