Created new plugin type custom_results. Added new plugin bang_redirect

AUTHORS.rst

@@ -124,3 +124,4 @@ generally made searx better:
 - @CaffeinatedTech
 - Robin Schneider @ypid
 - @splintah
+- Lukas van den Berk @lukasvdberk

docs/dev/plugins.rst

@@ -30,6 +30,14 @@ Example plugin
        ctx['search'].suggestions.add('example')
        return True
 
+Register your plugin
+====================
+
+To enable your plugin register your plugin in
+searx > plugin > __init__.py.
+And at the bottom of the file add your plugin like.
+``plugins.register(name_of_python_file)``
+
 Plugin entry points
 ===================