[Feature Request] OpenRouter Embeddings Support

[Joly0]

Is your feature request related to a problem? Please describe.
I tried setting up an embeddings model through openrouter, but got hit with an error, that this was not supported yet.

Describe the solution you'd like
Support for openrouter embedding models

Describe alternatives you've considered
None

Additional context
Add any other context or screenshots about the feature request here.

[jakehart99]

Feature: OpenRouter Embeddings Support

Support for OpenRouter embedding models would be a great addition out of the box. I have personally implemented this locally; it is quick and easy to add.

Implementation Details

1. Add openrouter as a supported provider in the _SUPPORTED_PROVIDERS list.
2. Add the following case to embeddings.py:

case "openrouter":
    from langchain_openai import OpenAIEmbeddings

    _embeddings = OpenAIEmbeddings(
        model=model,
        openai_api_key=os.getenv("OPENROUTER_API_KEY"),
        openai_api_base="https://openrouter.ai/api/v1",
        **embedding_kwargs,
    )