Update hello world example and add config example

examples/config/configurablebot.py

@@ -0,0 +1,25 @@
+from typing import Type
+
+from mautrix.util.config import BaseProxyConfig, ConfigUpdateHelper
+from maubot import Plugin, MessageEvent
+from maubot.handlers import command
+
+
+class Config(BaseProxyConfig):
+    def do_update(self, helper: ConfigUpdateHelper) -> None:
+        helper.copy("message")
+
+
+class DatabaseBot(Plugin):
+    async def start(self) -> None:
+        await super().start()
+        self.config.load_and_update()
+
+    @classmethod
+    def get_config_class(cls) -> Type[BaseProxyConfig]:
+        return Config
+
+    @command.new("getmessage")
+    async def handler(self, event: MessageEvent) -> None:
+        if event.sender != self.client.mxid:
+            await event.reply(self.config["message"])