ci: add MySQL to Dev Container config

Author: Genyus

.devcontainer/devcontainer.json

@@ -10,7 +10,8 @@
         "version": "none",
         "installMaven": "false",
         "installGradle": "false"
-      }
+      },
+      "ghcr.io/devcontainers-contrib/features/mysql-homebrew:1": {}
     },
 
     // Configure tool-specific properties.
@@ -31,6 +32,8 @@
       }
     },
 
-    "forwardPorts": [8080]
+    "forwardPorts": [8080],
+
+    "postStartCommand": "mysql.server start"
   }