Add cross-platform clipboard support on Tableview

Add option to copy selection to clipboard.

A code example (maybe there are other better ways), I don’t know what it’s like on Windows and Mac. But on Linux you need to use pyperclip to keep the data on the clipboard after closing the program. And on linux you also need to do this ‘update()’ twice and need the return 'break'

example:

import pyperclip

def tvw_item_ckick(self, event=None):
    self.tvw.selection()
    str_all_columns = ''
    for n in self.tvw.selection():
        str_columns = '\t'.join(self.tvw.item(n, 'values'))
        str_all_columns += f'''{str_columns}\n'''

    self.clipboard_clear()
    self.update()

    try:
        pyperclip.copy(str_all_columns)
    except TclError as e:
        raise e
    
    self.update()
    return 'break'

---

self.tvw.bind('<Control-c>', self.tvw_item_ckick)
self.tvw.bind('<Control-C>', self.tvw_item_ckick)

_Originally posted by @antrrax in https://github.com/israel-dryer/ttkbootstrap/issues/114#issuecomment-1004099982_

[israel-dryer]

Adding for reference: https://bugs.python.org/issue40452

[antrrax]

On Ubuntu/mint need to install xclip and xsel. But as it is something that is used frequently, it is already in my system post installation script, so I forget that it doesn’t come with the vanilla system.