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/utils.py

@@ -63,6 +63,14 @@ import warnings
 
 from .errors import InvalidArgument
 
+try:
+    import orjson
+except ModuleNotFoundError:
+    HAS_ORJSON = False
+else:
+    HAS_ORJSON = True
+
+
 __all__ = (
     'oauth_url',
     'snowflake_time',
@@ -468,8 +476,19 @@ def _bytes_to_base64_data(data: bytes) -> str:
     return fmt.format(mime=mime, data=b64)
 
 
-def to_json(obj: Any) -> str:
-    return json.dumps(obj, separators=(',', ':'), ensure_ascii=True)
+if HAS_ORJSON:
+
+    def to_json(obj: Any) -> str:  # type: ignore
+        return orjson.dumps(obj).decode('utf-8')
+
+    from_json = orjson.loads  # type: ignore
+
+else:
+
+    def to_json(obj: Any) -> str:
+        return json.dumps(obj, separators=(',', ':'), ensure_ascii=True)
+
+    from_json = json.loads
 
 
 def _parse_ratelimit_header(request: Any, *, use_clock: bool = False) -> float: