Add missing assignment operator overload for vec2=vec2

include/mtl/vec.hpp

@@ -160,6 +160,10 @@ public:
 		y = _y;
 	}
 
+	constexpr vec2& operator=(const vec2& other) noexcept {
+		vec2::operator=(other);
+		return *this;
+	}
 	constexpr vec2& operator=(const vec<2>& other) noexcept {
 		vec::operator=(other);
 		return *this;