Ender 3 NG v1.2 reinforced toolhead base

In a heated chamber, the belt mounts of the toolhead base tend to pull apart and warp the model.  This makes the belt loosen over time.  This improved version includes a bar in the middle of the toolhead base to prevent the part from warping under heat.

Here is a comparison of the original model on the left, with the strengthened version on the right:

Reinforcement bar added to the middle