Create Avatars for Chat Room members

[rene-grigory]

As part of the review of PR #385, the intent to create Avatars for members in the chat rooms was raised.

We could use the vcard API from converse.js to [update the profile information].(https://github.com/conversejs/converse.js/blob/master/src/headless/plugins/vcard.js#L291-L315). The vcard will expect a base64 encoded image. The desire is to use the jitsi user's avatar which can be accessed via the generic Room.

Here is the relevant section from the PR discussing this matter.