[enh] Update readme

Squelette de readme, pour éviter des readme sans infos.

README.md

@@ -1,11 +1,25 @@
-# YunoHost example app
+Example app for YunoHost
+==================
+
+[Yunohost project](https://yunohost.org/#/)
+
+Small description of the app
+
+https://example.com
 
 ## Usage
-- Add application source files into `sources` subfolder.
+- Fork this app before work on it.
+- Edit the source files into `sources` subfolder.
 - Edit `conf/nginx.conf` file to match application prerequisites.
 - Edit manifest with application specific information.
 - Edit the install, upgrade, remove, backup, restore scripts.
 - Add a LICENSE file for the package.
+- Edit this readme.
 
 **More information on the documentation page:**    
 https://yunohost.org/packaging_apps
+
+**Upgrade this package:**  
+sudo yunohost app upgrade --verbose example -u https://github.com/YunoHost-Apps/example_ynh
+
+**Multi-user:** Yes/No. How about the ldap and HTTP auth support.