filetree lookup: document RETURN value state (#11997)

* Clarify 'state' parameter description in filetree.py

Updated the description for the 'state' parameter to clarify entry types and their meanings.

* Apply suggestion from felixfontein related to description

Co-authored-by: Felix Fontein <felix@fontein.de>

---------

Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit 240ff65311)

plugins/lookup/filetree.py

@@ -80,8 +80,12 @@ _raw:
       description: The permissions the resulting file or directory.
       type: str
     state:
-      description: TODO.
+      description:
+        - Type of the resulting file or directory.
+        - V(directory) for a directory, V(file) for a regular file, V(link) for a symbolic link.
+        - Other file types are skipped and not returned.
       type: str
+      choices: [directory, file, link]
     owner:
       description: Name of the user that owns the file/directory.
       type: raw