"add a support here" feature

Sometimes, no matter how much I monkey with the sliders, I can’t get PreForm to add a support at a spot that needs one.

Some prints come out *perfect* except for one spot and the cause is clearly a missing support (or too few).

So the work flow would be:

  1. auto generate supports

  2. user inspects them

  3. If something looks “iffy”  they can say “add a support here” by clicking on a point on a surface of the part or something.