lastgenre: Docs for blacklist feature

Author: JOJ0

docs/plugins/lastgenre.rst

@@ -158,6 +158,33 @@ make sure any existing genres remain, set ``whitelist: no``).
     no`` means `not touching` existing tags anyway).
 
 
+Blacklisting Genres
+-------------------
+If you want to blacklist certain genres, they could simply be removed from the
+``whitelist``. This way, they will never be fetched from Last.fm. To only forbid them
+for a specific artist, the ``blacklist`` can be used. A possible ``blacklist`` file would
+look like this:
+
+.. code-block:: text
+
+    fracture:
+         ^(heavy|black|power|death)?\s?(metal|rock)$|\w+-metal\d*$
+        progressive metal
+    gilles peterson:
+        samba
+        bossa nova
+    *:
+        electronic
+
+A combination of regex patterns and plain genre names is possible. The ``*`` key matches
+all artists that are not explicitly defined, which is effectively the same as removing
+them from the whitelist (helpful if the default whitelist is desired to be kept).
+
+Set the ``blacklist`` option to the path of a blacklist file to enable this feature.
+
+.. attention::
+    Do not use single or double quotes around the genre names or regex patterns.
+
 
 Configuration
 -------------
@@ -210,6 +237,9 @@ configuration file. The available options are:
   tuning the plugin's settings and understanding how it works, but it can be
   quite verbose.
   Default: ``no``.
+- **blacklist**: The path to a blacklist file that contains genres to exclude from being
+  set as genres for specific artists. See `Blacklisting Genres`_ for more details.
+  Default: ``no``.
 
 Running Manually
 ----------------