Document exceptions and alternatives to using type (#6027)

Co-authored-by: Zedd Serjeant <Zedd.Serjeant@PumpkinEng.com.au>
Co-authored-by: Laurenz <laurmaedje@gmail.com>

crates/typst-library/src/foundations/ty.rs

@@ -39,11 +39,25 @@ use crate::foundations::{
 /// #type(image("glacier.jpg")).
 /// ```
 ///
-/// The type of `10` is `int`. Now, what is the type of `int` or even `type`?
+/// The type of `{10}` is `int`. Now, what is the type of `int` or even `type`?
 /// ```example
 /// #type(int) \
 /// #type(type)
 /// ```
+///
+/// Unlike other types like `int`, [none] and [auto] do not have a name
+/// representing them. To test if a value is one of these, compare your value to
+/// them directly, e.g:
+/// ```example
+/// #let val = none
+/// #if val == none [
+///   Yep, it's none.
+/// ]
+/// ```
+///
+/// Note that `type` will return [`content`] for all document elements. To
+/// programmatically determine which kind of content you are dealing with, see
+/// [`content.func`].
 #[ty(scope, cast)]
 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
 pub struct Type(Static<NativeTypeData>);