docs: document allow_non_static_methods in README and add test coverage

Author: Borda

README.rst

@@ -149,6 +149,7 @@ The following parameters will only be applied to decorators defined after `set_d
 *  `pickle_reload`
 *  `separate_files`
 *  `entry_size_limit`
+*  `allow_non_static_methods`
 
 These parameters can be changed at any time and they will apply to all decorators:
 

tests/test_core_lookup.py

@@ -8,6 +8,7 @@
 def test_get_default_params():
     params = get_global_params()
     assert sorted(vars(params).keys()) == [
+        "allow_non_static_methods",
         "allow_none",
         "backend",
         "cache_dir",