feature: Helper class for combining multiple memories

[creatorrr]

feature: Helper class for combining multiple memories

Usage:

conv_memory = ConversationBufferWindowMemory(
    memory_key="chat_history",
    input_key="input",
    output_key="bot_output",
    k=5,
    ai_prefix=ai_prefix,
    human_prefix=human_prefix,
)

additional_info_memory = AdditionalInfoMemory(
    memory_key="additional_info",
    read_key="output",
    include_intermediate_steps=True,
)

# Combined
memory = CombinedMemory(memories=[conv_memory, additional_info_memory])

[hwchase17]

boom i love it!

will probably add in an example notebook and then include in tmrws release

thank you!