Implement get_proxy() method in AbstractBot

[jumasheff]

Use services like https://www.proxyscan.io/

• [x] Add method
• [x] Make sure that the proxy is being applied: create a sample bot which should go to https://whatismyipaddress.com/ and check if the IP address shown is equal to the proxy IP.

[jumasheff]

This issue was addressed in https://github.com/AktanKasymaliev/Appointment-bot/pull/15