Group rust toolchain and dockerfile updates (#568)

Author: dani-garcia

.github/renovate.json

@@ -15,6 +15,11 @@
     "go": "1.21"
   },
   "packageRules": [
+    {
+      "groupName": "rust",
+      "matchManagers": ["custom.regex", "dockerfile"],
+      "matchDepNames": ["rust"]
+    },
     {
       "matchManagers": ["cargo"],
       "matchUpdateTypes": ["minor", "patch"],