Wrapping (modular) addition with a signed integer. Computes `self + rhs`,
wrapping around at the boundary of the type.
# Examples
Basic usage:
```
# use ::exint::primitive::*;
# ::exint::uint! {
assert_eq!(1_u24.wrapping_add_signed(2_i24), 3_u24);
assert_eq!(1_u24.wrapping_add_signed(-2_i24), u24::MAX);
assert_eq!((u24::MAX - 2_u24).wrapping_add_signed(4_i24), 1_u24);
# }
```