fix(drag): fix mouse drag on devices with touchscreen

[Ruslan207]

Description

If device has touchscreen, gridstack emulates mouse event from touch event + calls handler for pointer event. If user uses mouse, we don't need to manipulate with pointer event. So I check pointerType inside pointer events handlers.

Checklist

• Created tests which fail without the change (if possible)
• All tests passing (yarn test)
• Extended the README / documentation, if necessary

Issues fixed

#2413

[adumesny]

that is great, thank you.