[docs] update documentation with AUC-mu, average precision (#3627)

* [docs] update documentation with AUC-mu, average precision

* change formatting

docs/Features.rst

@@ -205,6 +205,10 @@ LightGBM supports the following metrics:
 
 -  Multi-class error rate
 
+-  AUC-mu ``(new in v3.0.0)``
+
+-  Average precision ``(new in v3.1.0)``
+
 -  Fair
 
 -  Huber