show_featured_artists.py and update publishing docs (#821)

* show_featured_artists.py and update publishing docs

* Don't update version

Co-authored-by: Stéphane Bruckert <contact@stephanebruckert.com>

examples/show_featured_artists.py

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+# Shows all artists featured on an album
+
+# usage: featured_artists.py spotify:album:[album urn]
+
+from spotipy.oauth2 import SpotifyClientCredentials
+import sys
+import spotipy
+from pprint import pprint
+
+if len(sys.argv) > 1:
+    urn = sys.argv[1]
+else:
+    urn = 'spotify:album:5yTx83u3qerZF7GRJu7eFk'
+
+sp = spotipy.Spotify(client_credentials_manager=SpotifyClientCredentials())
+album = sp.album(urn)
+
+featured_artists = set()
+
+items = album['tracks']['items']
+
+for item in items:
+    for ele in item['artists']:
+        if 'name' in ele:
+            featured_artists.add(ele['name'])
+
+pprint(featured_artists)