Draft: Resolve "Improve README"

Closes #19 (closed)

README.md

-# spotify
+# Spotify playlist generator
 
-# Register app
+Create fresh playlists from selected top played artists or existing playlists.
 
-<https://developer.spotify.com/dashboard/applications>
+Playlists are generated as public Spotify playlists, with 50 tracks (~3 hours), from your personal Spotify recommendations.
 
-App name:
-    Spotify playlist manager
+## Generate fresh playlist form artists
 
-Add description:
-    Application to help create/update playlists from other playlists or selected artists/tracks.
-    Something like "radios", but more personalized.
+From the list of your top played artists.
 
-Client ID:
-    41597dbeb0b3403caa28e7e428e0c9b2
+-   pick one or several artists in list
+-   click on "generate"
+-   a fresh playlist is generated with recommendations from each artist in pick ones
 
-Client Secret:
-    <hidden>
+You can choose if you want all recommendations, or only the ones with picked artists.
+
+A direct button can help to randomly pick artists.
+
+## Generate fresh playlist from existing playlists
+
+-   pick one or several playlist in list
+-   click on "generate"
+-   a fresh playlist is generated with recommendations from each track in picked playlists
+
+You can choose if you want all recommendations, or only the ones with artists in picked playlists.