Resuming a failed connection

[n7st]

Investigate the actions taken when the client disconnects and attempts to resume.

Discord::Client::connect():

$self->connection->on(finish => sub {
    $self->connection->close();
    $self->_run_external_subroutine('finish', @_);
    $self->connect();
});

On "finish", the reconnection should send parameters for "resuming" the connection to Discord::Client::hello() in order to collect the old session ID and gracefully resume the existing connection rather than running a hard disconnect and connect.

Presently, the resume does not block the AnyEvent loop.