Fixes Unity editor viewport mousewheel

EditorCameraZoomWithScrollWheel.cs

#if UNITY_2019_1_OR_NEWER
using UnityEditor;
using UnityEngine;

[InitializeOnLoad]
public class EditorCameraZoomWithScrollWheel
{
    private const float CAMERA_SPEED = -0.25f;

    private static bool rmbDown = false;

    static EditorCameraZoomWithScrollWheel()
    {
        SceneView.beforeSceneGui -= OnScene;
        SceneView.beforeSceneGui += OnScene;
    }

    private static void OnScene(SceneView scene)
    {
        Event e = Event.current;
        if (e.isMouse && e.button == 1)
        {
            if (e.type == EventType.MouseDown)
                rmbDown = true;
            else if (e.type == EventType.MouseUp)
                rmbDown = false;
        }

        if (e.isScrollWheel && rmbDown)
        {
            Vector3 pivot = scene.pivot;
            pivot += scene.camera.transform.forward * (e.delta.y * CAMERA_SPEED);
            scene.pivot = pivot;

            e.Use();
        }
    }
}
#endif