Create a Voila room on Gitter / Element / Matrix

[jtpio]

Problem

Currently the Gitter badge in the README redirects to the QuantStack/Lobby room on Gitter:

While this room is public, it would make sense to send users and contributors to a room with "Voila" in its name.

Suggested Improvement

Creating a new room is fairly easy and quick, and does not cost anything.

Otherwise, redirect to the existing jupyter/jupyter room on Gitter.

It's also worth noting there has been discussions within the Jupyter community to find a new tool for instant messaging, although nothing has been decided yet as of today: jupyter/governance#182

[jtpio]

The issue template could also be updated here: https://github.com/voila-dashboards/.github/blob/19c1dcacc4104a5d970e58eb59a9b63cbed71cb6/.github/ISSUE_TEMPLATE/config.yml#L5