LibGfx: Add unary operator-() to Vector2/3/4

Author: https://github.com/Quaker762
Commit: https://github.com/SerenityOS/serenity/commit/53ed93d9095
Pull-request: https://github.com/SerenityOS/serenity/pull/11905
Reviewed-by: https://github.com/BertalanD
Reviewed-by: https://github.com/IdanHo ✅
Reviewed-by: https://github.com/gmta
Reviewed-by: https://github.com/sunverwerth ✅

Userland/Libraries/LibGfx/Vector2.h

@@ -50,6 +50,11 @@ public:
         return Vector2(m_x - other.m_x, m_y - other.m_y);
     }
 
+    constexpr Vector2 operator-() const
+    {
+        return Vector2(-m_x, -m_y);
+    }
+
     constexpr Vector2 operator*(const Vector2& other) const
     {
         return Vector2(m_x * other.m_x, m_y * other.m_y);

Userland/Libraries/LibGfx/Vector3.h

@@ -55,6 +55,11 @@ public:
         return Vector3(m_x - other.m_x, m_y - other.m_y, m_z - other.m_z);
     }
 
+    constexpr Vector3 operator-() const
+    {
+        return Vector3(-m_x, -m_y, -m_z);
+    }
+
     constexpr Vector3 operator*(const Vector3& other) const
     {
         return Vector3(m_x * other.m_x, m_y * other.m_y, m_z * other.m_z);

Userland/Libraries/LibGfx/Vector4.h

@@ -60,6 +60,11 @@ public:
         return Vector4(m_x - other.m_x, m_y - other.m_y, m_z - other.m_z, m_w - other.m_w);
     }
 
+    constexpr Vector4 operator-() const
+    {
+        return Vector4(-m_x, -m_y, -m_z, -m_w);
+    }
+
     constexpr Vector4 operator*(const Vector4& other) const
     {
         return Vector4(m_x * other.m_x, m_y * other.m_y, m_z * other.m_z, m_w * other.m_w);