Improved filters system

- `RoomEventData` is renamed to `EventContext` and moved to context.py
- `EventContext.filter` is removed
- Added context variables system which improves type hints and simplifies callbacks code
- `BodyCommandFilter` sets context variables from now on
- Added `super().__call__` invocation to filters implements in base.py
- Examples are updated to include required changes

examples/echo_bot.py

@@ -9,21 +9,13 @@ import asyncio
 import os
 import logging
 
-from mab import (
-    MatrixBot,
-    MatrixBotConfig,
-    RoomEventData,
-    BodyExistsFilter,
-    MessageTypeFilter,
-    SenderIsBotFilter,
-    MessageType
-)
+from mab import *
 
 from _environment import check_environment
 
-async def on_text_message(data: RoomEventData) -> None:
+async def on_text_message(ctx: EventContext) -> None:
     """This callback is called when a text message arrives."""
-    await data.bot.send_text(data.room, data.event.body) # type: ignore
+    await ctx.bot.send_text(ctx.room, ctx[CTX_BODY])
 
 async def main() -> None:
     """Application entry point"""