added !book

[cyanliu]

should hopefully match on phrases like 'what books do you recommend'

[asottile]

$ python3 -m bot --test 'what book would you recommend?'
[17:05]<username> what book would you recommend?
Traceback (most recent call last):
  File "/usr/lib/python3.10/runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.10/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "/home/asottile/workspace/anthonywritescode/twitch-chat-bot/bot/__main__.py", line 6, in <module>
    raise SystemExit(main())
  File "/home/asottile/workspace/anthonywritescode/twitch-chat-bot/bot/main.py", line 344, in main
    asyncio.run(
  File "/usr/lib/python3.10/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/usr/lib/python3.10/asyncio/base_events.py", line 649, in run_until_complete
    return future.result()
  File "/home/asottile/workspace/anthonywritescode/twitch-chat-bot/bot/main.py", line 314, in chat_message_test
    result = await handler(config, match)
  File "/home/asottile/workspace/anthonywritescode/twitch-chat-bot/bot/plugins/smarts.py", line 17, in _base
    return await COMMANDS[cmd](config, msg)
KeyError: '!book'