Configure Renovate to track libversion submodule releases

- Enable git-submodules manager in renovate.json
- Set submodule branch to tag 3.0.4 so Renovate updates to new tags

Author: xz-dev

.gitmodules

@@ -1,3 +1,4 @@
 [submodule "libversion"]
 	path = libversion
 	url = https://github.com/repology/libversion.git
+	branch = 3.0.4

renovate.json

@@ -2,5 +2,8 @@
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
   "extends": [
     "config:recommended"
-  ]
+  ],
+  "git-submodules": {
+    "enabled": true
+  }
 }