Add support for a configuration file.

src/bot_main.py

@@ -1,4 +1,7 @@
 import asyncio
+import json
+import os
+import sys
 
 try:
     # uvloop doesn't work on Windows, therefore an optional dependency
@@ -7,5 +10,13 @@ try:
 except ImportError:
     pass
 
-from pluralkit import bot
-bot.run()
+with open(sys.argv[1] if len(sys.argv) > 1 else "pluralkit.conf") as f:
+    config = json.load(f)
+
+if "database_uri" not in config and "database_uri" not in os.environ:
+    print("Config file must contain key 'database_uri', or the environment variable DATABASE_URI must be present.")
+elif "token" not in config and "token" not in os.environ:
+    print("Config file must contain key 'token', or the environment variable TOKEN must be present.")
+else:
+    from pluralkit import bot
+    bot.run(os.environ.get("TOKEN", config["token"]), os.environ.get("DATABASE_URI", config["database_uri"]), int(config.get("log_channel", 0)))