Feature or enhancement

CallTips was originally an object of type tk.Label, I hack it into type tk.Text, keeping the size and content unchanged, so the text in calltip can be SELECTED.

Previous discussion

Discuss at: https://discuss.python.org/t/i-made-some-improvement-for-idle-can-i-contribute-to-idlelib-library-in-python-project

Usage: https://github.com/znsoooo/IDLE-Advance

Implementation: https://github.com/znsoooo/IDLE-Advance/blob/master/idlealib/CalltipSelect.py