Add a drag_and_drop() method

Add drag_and_drop(drag_selector, drop_selector)

• Full method call:

self.drag_and_drop(drag_selector, drop_selector,
    drag_by=By.CSS_SELECTOR, drop_by=By.CSS_SELECTOR,
    timeout=None)

Other updates:

• If using a feature that uses Chrome extensions, then Incognito / Guest Mode won't be used, even when using --incognito or --guest.
• Update ad-blocking
• Update proxy_list
• Add an example test for Drag & Drop - https://github.com/seleniumbase/SeleniumBase/blob/master/examples/test_drag_and_drop.py

Update Python dependencies:

• cryptography==3.0
• pdfminer.six==20200720