chore(deps): disable Rust toolchain updates (#375)

Author: chenjiahan

.github/renovate.json

@@ -2,6 +2,11 @@
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
   "extends": ["github>rstackjs/renovate"],
   "packageRules": [
+    {
+      "description": "Disable Rust toolchain updates",
+      "matchManagers": ["rust-toolchain"],
+      "enabled": false
+    },
     {
       "description": "Disable TypeScript updates in Svelte and Vue templates until svelte-check, svelte2tsx, and vue-tsc support TypeScript 7",
       "matchManagers": ["npm"],