Blender Git Loki

Fix T50565: Planar constraints don't work properly with non-Blender key configurations

The issue was introduced by 4df75e5 and seems we just need to explicitly
add new keymap item now.

There is still some difference from old behavior, which is planar transform
is using precision movement since e138cde and here i don't see nice solution
currently: the change was requested here in the studio and it's just a
conflict in picking shift key for something which is not supposed to be
accurate.

At least now it's possible to invoke planar constraint and simply unhold
shift.