feat(service): Add Zulip service

[nikoksr]

Describe the missing service. Please provide useful links.

Add new service for zulip. API docs can be found here.

[saisumith770]

@nikoksr I've looked through libraries for zulip in golang, most of them were unmaintained so I wrote a client along with a wrapper for notify. I've created a PR at #711 . If any changes are required do let me know!