DOC: Add documentation for integrations supported with Genkit and LangChain

[pranav-kural]

Checklist

• [X] I added a very descriptive title to this issue.
• [X] I included a link to the documentation page I am referring to (if applicable).

Issue with current documentation:

Missing documentation on adding plugins when setting up Genkit.

Also, missing documentation on extending data loaders with LangChain.

Should create two separate pages under integrations, one each for Genkit and LangChain.

https://qvikchat.pkural.ca/integrations/genkit https://qvikchat.pkural.ca/integrations/langchain

Idea or request for content:

No response

[pranav-kural]

Documentation updated now