Automate bit.ly creation to the meetup event page link

[girikuncoro]

Is your feature request related to a problem? Please describe.
For every meetup event, we distribute shorten link to meetup event page, since the url is too long to be distributed. We use bit.ly that redirects to the meetup event page which is created manually for every meetup. We need to automate this, as per #4

Describe the solution you'd like
Automate creation bit.ly by calling the bit.ly API, integrate as subcommand of existing https://github.com/cloudnative-id/meetups/tree/master/generator tool

Additional context
Since meetup event page creation is still done manually, we can assume the page already exists for the meetup. Behavior when running the tool:

bin/generator <meetup-directory> <event-url>

Example:

bin/generator bandung https://www.meetup.com/Kubernetes-and-Cloud-Native-Bandung/events/267202957

We can iterate next step to only pass the event id 267202957 by mapping the meetup URL in meetup.yaml