docs: add barebones example on how to find items by a specific artist.

Jellyfin.Plugin.SmartPlaylist/PluginConfiguration.cs

@@ -39,7 +39,8 @@ namespace Jellyfin.Plugin.SmartPlaylist {
               (define all-genres (lambda (want have) (all (lambda (x) (is-genre x have)) want)))
               (define any-genres (lambda (want have) (any (lambda (x) (is-genre x have)) want)))
               (define get-name (lambda (x) (car (getitems x "Name"))))
-              (define find-parent (lambda (typename) (invoke-generic item "FindParent" nil (list typename)))))
+              (define find-parent (lambda (typename) (invoke-generic item "FindParent" nil (list typename))))
+              (define find-artist (lambda nil (find-parent "MediaBrowser.Controller.Entities.Audio.MusicArtist, MediaBrowser.Controller"))))
             """;
         }
         public string InitialProgram { get; set; }

examples.md

@@ -25,3 +25,31 @@
         (is-genre "electro" g)
         (is-genre "swing" g)))
   ```
+
+- `All of Seeed`: A playlist containing all items by artist `Seeed`,
+  useless, since you also can just navigate to the artist to play all
+  their songs, but a good example.
+  ```
+  Id: Seeed
+  Name: Seeed
+  Program: |
+    (let
+      (parent
+        (invoke-generic item "FindParent" nil (list "MediaBrowser.Controller.Entities.Audio.MusicArtist, MediaBrowser.Controller")))
+      (cond
+        ((null parent) nil)
+        (t (string= (car (getitems parent "Name")) "Haller"))))
+  ```
+  or simplified with definitions contained in the preamble:
+  ```
+  Id: Seeed
+  Name: Seeed
+  Program: |
+    (let
+      (parent
+        (find-parent "MediaBrowser.Controller.Entities.Audio.MusicArtist, MediaBrowser.Controller"))
+      (cond
+        ((null parent) nil)
+        (t (string= (car (getitems parent "Name")) "Seeed"))))
+
+  ```