`GrowArrow` for `Arrow3D`

[PhotonSpheres]

Enhancement proposal

GrowArrow() only works for class Arrow, not for Arrow3D since it utilizes the own scale method of Arrow. This scale method relies on Arrow being a TipableVMobject, which Arrow3D is not. I have 3 suggestions:

• Do nothing and state that GrowArrow is only meant for Arrow. Then I would implement an error when a class Arrow3D is passed.
• Implement the changes I proposed in PR Fixing GrowArrow() #1668, that is, if an Arrow3D is passed just use the normal scale. This still looks good.
• Build an own scale method for Arrow3D. This seems quite time-consuming since one would have to think about implementing the tipable stuff for 3D Mobjects. This might be good in the future but would be too much for me to handle right now.

Thoughts are welcome!

Additional comments