docs: update version info

Author: yyx990803

Diff for: docs/en/SUMMARY.md

@@ -1,7 +1,7 @@
 # vue-router 2
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-> Note: vue-router@2.x only works with Vue 2.x. Docs for 0.7.x is [here](https://github.com/vuejs/vue-router/tree/1.0/docs/en).
-<!--/email_off-->
+
+> Note: for TypeScript users, vue-router@>= 3.0 requires vue@>=2.5, and vice versa.
+
 **[Release Notes](https://github.com/vuejs/vue-router/releases)**
 
 - [Installation](installation.md)