Repo improvements

- Improved README.md
- Added examples
- Added `session_storage/` to .gitignore so that examples do not introduce leftover files after execution

examples/echo_bot.py

@@ -0,0 +1,51 @@
+"""
+This example implements Matrix bot that echoes all text messages it receives.
+
+It uses environment variables to specify authorization data. Use Ctrl+C to stop
+the bot.
+"""
+
+import asyncio
+import os
+import logging
+
+from mab import (
+    MatrixBot,
+    MatrixBotConfig,
+    RoomEventData,
+    BodyExistsFilter,
+    MessageTypeFilter,
+    SenderIsBotFilter,
+    MessageType
+)
+
+from _environment import check_environment
+
+async def on_text_message(data: RoomEventData) -> None:
+    """This callback is called when a text message arrives."""
+    await data.bot.send_text(data.room, data.event.body) # type: ignore
+
+async def main() -> None:
+    """Application entry point"""
+    logging.basicConfig(level=logging.INFO)
+    logging.getLogger("nio").setLevel(logging.CRITICAL+1)
+    check_environment()
+
+    config = MatrixBotConfig(
+        matrix_homeserver_url=os.environ["MATRIX_HOMESERVER"],
+        matrix_username_localpart=os.environ["MATRIX_USERNAME"],
+        storage_directory="session_storage"
+    )
+    bot = MatrixBot(config)
+    bot.add_callback(
+        ~SenderIsBotFilter() & BodyExistsFilter() & MessageTypeFilter(MessageType.TEXT),
+        on_text_message)
+
+    # run until Ctrl+C
+    try:
+        await bot.run()
+    except asyncio.CancelledError:
+        pass
+
+if __name__ == "__main__":
+    asyncio.run(main())