feat: update README.md

Author: gazenw

README.md

@@ -10,6 +10,7 @@ This project is a fork of [lukechampine/uint128](https://github.com/lukechampine
    - Add `AddOverflow`, `Add64Overflow`, `SubOverflow`, `Sub64Overflow`, `MulOverflow`, `Mul64Overflow` functions which returns additional boolean indicating whether the operation overflowed. The original functions now ignores overflow instead of panicking.
    - Change `FromBig` function behaviour to return errors instead of panicking.
 2. Add conversion functions `Uint64()`, `Uint32()`, `Uint16()`, `Uint8()` to convert `Uint128` to native types.
+3. Add functions `IsUint64()`, `IsUint32()`, `IsUint16()`, `IsUint8()` to check if `Uint128` can be converted to native types without overflow.
 
 `uint128` provides a high-performance `Uint128` type that supports standard arithmetic
 operations. Unlike `math/big`, operations on `Uint128` values always produce new values