Fix long description content type (#270)

setup.py

@@ -1,5 +1,10 @@
+from pathlib import Path
+
 from setuptools import setup
 
+this_directory = Path(__file__).parent
+long_description = (this_directory / "README.md").read_text()
+
 setup(
     name="PySwitchbot",
     packages=["switchbot", "switchbot.devices", "switchbot.adv_parsers"],
@@ -12,6 +17,8 @@ setup(
     ],
     version="0.53.1",
     description="A library to communicate with Switchbot",
+    long_description=long_description,
+    long_description_content_type="text/markdown",
     author="Daniel Hjelseth Hoyer",
     url="https://github.com/sblibs/pySwitchbot/",
     license="MIT",