Update Description

[SnowMB]

Hey,

maybe we should update the description a little bit instead of just linking to IndieHosters/Nextcloud:

• Explain that this container does not include a webserver and needs one in front (even to run locally)
• How to update
• etc.

[pierreozoux]

Agreed :)

Could you PR?

here a nice example from piwik php-fpm: https://github.com/piwik/docker-piwik (It just got updated).