🔧(renovate) add dimail-api to renovate scope

Dimail-api is currently outside of renovate' scope, which resulted in us having
to check and update dimail's image manually or, if failing to, discovering new
behaviors by chance or by errors in production. This should fix it.

renovate.json

@@ -14,6 +14,11 @@
       "groupName": "ignored js dependencies",
       "matchManagers": ["npm"],
       "matchPackageNames": ["fetch-mock", "node", "node-fetch", "eslint", "@hookform/resolvers"]
+    },
+    {
+      "groupName": "docker-compose dependencies",
+      "matchManagers": ["docker-compose"],
+      "matchPackageNames": ["dimail-api"]
     }
   ]
 }