Update the guide

Author: Liamolucko

guide/src/SUMMARY.md

@@ -52,7 +52,7 @@
     - [Imported JavaScript Types](./reference/types/imported-js-types.md)
     - [Exported Rust Types](./reference/types/exported-rust-types.md)
     - [`JsValue`](./reference/types/jsvalue.md)
-    - [`Box<[JsValue]>`](./reference/types/boxed-jsvalue-slice.md)
+    - [`Box<[T]>` and `Vec<T>`](./reference/types/boxed-slices.md)
     - [`*const T` and `*mut T`](./reference/types/pointers.md)
     - [Numbers](./reference/types/numbers.md)
     - [`bool`](./reference/types/bool.md)

guide/src/reference/types/boxed-jsvalue-slice.md renamed to guide/src/reference/types/boxed-slices.md

@@ -1,10 +1,19 @@
-# `Box<[JsValue]>`
+# `Box<[T]>` and `Vec<T>`
 
 | `T` parameter | `&T` parameter | `&mut T` parameter | `T` return value | `Option<T>` parameter | `Option<T>` return value | JavaScript representation |
 |:---:|:---:|:---:|:---:|:---:|:---:|:---:|
 | Yes | No | No | Yes | Yes | Yes | A JavaScript `Array` object |
 
-Boxed slices of imported JS types and exported Rust types are also supported. `Vec<T>` is supported wherever `Box<[T]>` is.
+You can pass boxed slices and `Vec`s of several different types to and from JS:
+
+- `JsValue`s.
+- Imported JavaScript types.
+- Exported Rust types.
+- `String`s.
+
+[You can also pass boxed slices of numbers to JS](boxed-number-slices.html),
+except that they're converted to typed arrays (`Uint8Array`, `Int32Array`, etc.)
+instead of regular arrays.
 
 ## Example Rust Usage