doc: add missing float32/float64 FFI type names

`ToFFIType()` accepts `float32` and `float64` as aliases for `float`
and `double`, and both names already appear in the `ffi.types`
constants list further down the same page, but they were missing from
the list of supported type names.

Also split `char` onto its own line. Unlike `u8`, `uint8` and `bool`,
which always map to `ffi_type_uint8`, `char` maps to either
`ffi_type_sint8` or `ffi_type_uint8` depending on the platform C ABI,
as the paragraph below the list already explains.

Signed-off-by: Soul Lee <alus20x@gmail.com>
PR-URL: #64874
Refs: #62892
Refs: #64848
Reviewed-By: René <contact.9a5d6388@renegade334.me.uk>
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Ulises Gascón <ulisesgascongonzalez@gmail.com>

Author: soulee-dev

doc/api/ffi.md

@@ -62,16 +62,17 @@ FFI signatures use string type names.
 Supported type names:
 
 * `void`
+* `char`
 * `i8`, `int8`
-* `u8`, `uint8`, `bool`, `char`
+* `u8`, `uint8`, `bool`
 * `i16`, `int16`
 * `u16`, `uint16`
 * `i32`, `int32`
 * `u32`, `uint32`
 * `i64`, `int64`
 * `u64`, `uint64`
-* `f32`, `float`
-* `f64`, `double`
+* `f32`, `float`, `float32`
+* `f64`, `double`, `float64`
 * `pointer`, `ptr`
 * `string`, `str`
 * `buffer`