Use orjson when already installed or with speedups extra (#466)

* Use orjson when already installed

* Use orjson when already installed

* fix patch target

* fix patch target

* add speedups extra

* Update README.md

* Update README.md

kasa/json.py

@@ -0,0 +1,15 @@
+"""JSON abstraction."""
+
+try:
+    import orjson
+
+    def dumps(obj, *, default=None):
+        """Dump JSON."""
+        return orjson.dumps(obj).decode()
+
+    loads = orjson.loads
+except ImportError:
+    import json
+
+    dumps = json.dumps
+    loads = json.loads