Add code from pylast #407 to readme

Describe authentication with OAuth token

README.md

@@ -85,6 +85,32 @@ network = pylast.LastFMNetwork(
     password_hash=password_hash,
 )
 
+# You can also authenticate with a session key
+SESSION_KEY_FILE = os.path.join(os.path.expanduser("~"), ".session_key")
+network = pylast.LastFMNetwork(API_KEY, API_SECRET)
+if not os.path.exists(SESSION_KEY_FILE):
+    skg = pylast.SessionKeyGenerator(network)
+    url = skg.get_web_auth_url()
+
+    print(f"Please authorize this script to access your account: {url}\n")
+    import time
+    import webbrowser
+
+    webbrowser.open(url)
+
+    while True:
+        try:
+            session_key = skg.get_web_auth_session_key(url)
+            with open(SESSION_KEY_FILE, "w") as f:
+                f.write(session_key)
+            break
+        except pylast.WSError:
+            time.sleep(1)
+else:
+    session_key = open(SESSION_KEY_FILE).read()
+
+network.session_key = session_key
+
 # Now you can use that object everywhere
 track = network.get_track("Iron Maiden", "The Nomad")
 track.love()