Allow use of orjson instead of json

The difference in speed seems negligible at start up, which is when
most time is taken for actually parsing JSON. I could potentially be
missing something but profiling didn't point to any discernable
difference.

discord/gateway.py

@@ -25,7 +25,6 @@ DEALINGS IN THE SOFTWARE.
 import asyncio
 from collections import namedtuple, deque
 import concurrent.futures
-import json
 import logging
 import struct
 import sys
@@ -421,7 +420,7 @@ class DiscordWebSocket:
             msg = self._zlib.decompress(self._buffer)
             msg = msg.decode('utf-8')
             self._buffer = bytearray()
-        msg = json.loads(msg)
+        msg = utils.from_json(msg)
 
         log.debug('For Shard ID %s: WebSocket Event: %s', self.shard_id, msg)
         self._dispatch('socket_response', msg)
@@ -882,7 +881,7 @@ class DiscordVoiceWebSocket:
         # This exception is handled up the chain
         msg = await asyncio.wait_for(self.ws.receive(), timeout=30.0)
         if msg.type is aiohttp.WSMsgType.TEXT:
-            await self.received_message(json.loads(msg.data))
+            await self.received_message(utils.from_json(msg.data))
         elif msg.type is aiohttp.WSMsgType.ERROR:
             log.debug('Received %s', msg)
             raise ConnectionClosed(self.ws, shard_id=None) from msg.data