Add random server option

[Martin-K24]

I'm not sure how to do it extactly actions.py.
but... it would look something like this.

Add "random-server" option in actions.py that uses import random to select a random server from list in config.
I'm sure it would be something like how mirror works but without spliting it and using random imported into it

Then update connection option -S or --random-server and default configuration added to None in cli.py.

    ## Connection options
    send_parser.add_argument("-s", "--server", default=argparse.SUPPRESS, help="Instance URL (default: https://paste.i2pd.xyz/)")
    send_parser.add_argument("-S", "--random-server", default=argparse.SUPPRESS, help="Select random URL instance from server_list in config file")

    # default configuration
    CONFIG = {
        'server': 'https://paste.i2pd.xyz/',
        'server_list': None,

Config file option in ~/.config/pbincli/pbincli.conf

server_list=server1,server2,server3,etc