Add audio and video calls option in zulip.

Zulip is an opensource and android application which is community built group chat platform, optimized around helping organizations communicate efficiently.

I am proposing that there should be options available for audio and video calls.!
The options for audio and video calls should be implimented here along side the message option.

I have presented an example of how this should look in the image above.

We can communicate in a better way by these options. There will be a lessor communication gap between two users, I would like to see these options in zulip. We can also save our time by directly communicating through audio and video calls.

Thanks