Can only select text with a right click and cannot drag mouse to select on demand

[LaurentDumont]

Describe the bug
Cannot highlight text with mouse in terminal.

To Reproduce
Steps to reproduce the behavior:

1. Render py-cui panels
2. Try to select a portion of text with left mouse button
3. You cannot select the text for copy

Expected behavior
Should be able to select text by dragging the mouse

Environment:

• OS: Mac Monterey
• Terminal: iterm
• Version: 0.1.4

I am not sure if this is actually a bug but it seems a bit strange that I cannot select the rendered text like a normal terminal. 🤔

[jwlodek]

I think this is a side effect of how py_cui currently handles mouse events, since it captures mouse presses/holds etc. We might need a function to override this behavior. Something like allow_highlighting maybe?