add mediaType keyword to agents method

Thanks @JonnyWong16

Author: blacktwin

plexapi/server.py

@@ -184,9 +184,11 @@ def account(self):
         data = self.query(Account.key)
         return Account(self, data)
 
-    def agents(self):
+    def agents(self, mediaType=None):
         """ Returns the `:class:`~plexapi.media.Agent` objects this server has available. """
         key = '/system/agents'
+        if mediaType:
+            key += '?mediaType=%s' % mediaType
         return self.fetchItems(key)
 
     def createToken(self, type='delegation', scope='all'):