Adds hash support for Vector2, Vector3, and Vector4

Implements `std::hash` specialization for `omath::Vector2`, `omath::Vector3`, and `omath::Vector4` with float components.

This enables usage of these vector types as keys in hash-based containers, such as `std::unordered_map` and `std::unordered_set`.

include/omath/linear_algebra/vector3.hpp

@@ -273,6 +273,7 @@ namespace omath
 
 template<> struct std::hash<omath::Vector3<float>>
 {
+    [[nodiscard]]
     std::size_t operator()(const omath::Vector3<float>& vec) const noexcept
     {
         std::size_t hash = 0;