Add getting started section to docs
Add Getting started section to documentation: https://notifications.docs.cern.ch/
Subsections:
- Notifications overview (features, what can be used for and so on)
- Creating a channel
- Adding members
- Sending a notification
- Setting your preferences
Eg
- https://docs.mattermost.com/about/product.html
- https://kubernetes.docs.cern.ch/docs/getting-started/
Let's keep it short, and user friendly.