add DOM interface info to Typing Template Refs (#2463)

Provide information and a place to find the right dom interface

Author: albertlast

src/guide/typescript/composition-api.md

@@ -352,6 +352,8 @@ onMounted(() => {
 </template>
 ```
 
+To get the right DOM interface you can check pages like [MDN](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input#technical_summary).
+
 Note that for strict type safety, it is necessary to use optional chaining or type guards when accessing `el.value`. This is because the initial ref value is `null` until the component is mounted, and it can also be set to `null` if the referenced element is unmounted by `v-if`.
 
 ## Typing Component Template Refs {#typing-component-template-refs}