docs: clarify that each blocks use Array.from (#17691)

closes #17227

documentation/docs/03-template-syntax/03-each.md

@@ -13,7 +13,7 @@ tags: template-each
 {#each expression as name, index}...{/each}
 ```
 
-Iterating over values can be done with an each block. The values in question can be arrays, array-like objects (i.e. anything with a `length` property), or iterables like `Map` and `Set`— in other words, anything that can be used with `Array.from`.
+Iterating over values can be done with an each block. The values in question can be arrays, array-like objects (i.e. anything with a `length` property), or iterables like `Map` and `Set`. (Internally, they are converted to arrays with [`Array.from`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from).)
 
 If the value is `null` or `undefined`, it is treated the same as an empty array (which will cause [else blocks](#Else-blocks) to be rendered, where applicable).