Introduce hex and binary literals before the signed type rule

The page jumped from a one-line mention of hex straight into the
signed-type edge case. Restructure: explain what hex and binary
prefixes are and that the three notations are equivalent, then
the signed range rule follows naturally.

Author: SeanTAllen

docs/expressions/literals.md

@@ -34,15 +34,17 @@ It is possible to help the compiler determine the concrete type of the literal u
 --8<-- "literals-numeric-typing.pony"
 ```
 
-Integer literals can be given as decimal, hexadecimal or binary:
+### Hex and Binary Literals
+
+Integer literals can be written in hexadecimal with the `0x` prefix or binary with the `0b` prefix. They represent the same values as their decimal equivalents:
 
 ```pony
 --8<-- "literals-number-types.pony:3:5"
 ```
 
-### Hex Literals on Signed Types
+All three lines above assign 1024 to an I32.
 
-A hex literal like `0x80000000` looks like it should fit in an I32, but it is the positive value 2,147,483,648 — one more than I32's maximum of 2,147,483,647. The compiler rejects any literal whose value exceeds the signed type's maximum:
+Hex and binary literals are always positive values. The compiler rejects a literal whose value exceeds the signed type's maximum. A hex literal like `0x80000000` is the positive value 2,147,483,648, one more than I32's maximum of 2,147,483,647:
 
 ```pony
 let x: I32 = 0x80000000