docs: update the readme to note Google provided integrations

[averikitsch]

No description provided.

[eyurtsev]

2 requests:

1. Could you add the standard test suite to the google packages and confirm that they pass the tests? It should be very quick to confirm and run the tests (~8 lines of code).

https://github.com/langchain-ai/langchain-postgres/blob/main/tests/unit_tests/test_vectorstore_standard_tests.py

2. Could you document the lack of db agnostic filtering support? it's a feature a lot of users look for (easy filtering). I think if we're recommending something from this package, users will likely expect feature parity

[averikitsch]

1. We will have to make a few updates to our vector store ie support the method (a)get_by_ids() and support Document id fields and in metadata.
2. I have added the note in the Readme. We will also look to support this

[efriis]

@averikitsch could you confirm those tests are in and passing? If so happy to merge, otherwise will probably close until they do!

We also have a guide on implementing them now: https://python.langchain.com/docs/contributing/how_to/integrations/standard_tests/

[ccurme]

Closing but will re-open pending response from @averikitsch.

[averikitsch]

I will re-open this PR when we have updated the test. Thanks!