Allow initializing HuggingFaceEmbeddings from the cached weight
### Feature request


### Suggestion

The only change has only a few lines in `__init__()`,

```python
class HuggingFaceEmbeddings(BaseModel, Embeddings):
    """Wrapper around sentence_transformers embedding models.

    To use, you should have the ``sentence_transformers`` python package installed.

    Example:
        .. code-block:: python

            from langchain.embeddings import HuggingFaceEmbeddings
            model_name = "sentence-transformers/all-mpnet-base-v2"
            hf = HuggingFaceEmbeddings(model_name=model_name)
    """

    client: Any  #: :meta private:
    model_name: str = DEFAULT_MODEL_NAME
    """Model name to use."""

    def __init__(self, cache_folder=None, **kwargs: Any):
        """Initialize the sentence_transformer."""
        super().__init__(**kwargs)
        try:
            import sentence_transformers
            self.client = sentence_transformers.SentenceTransformer(model_name_or_path=self.model_name, cache_folder=cache_folder)
        except ImportError:
            raise ValueError(
                "Could not import sentence_transformers python package. "
                "Please install it with `pip install sentence_transformers`."
            )

    class Config:
        """Configuration for this pydantic object."""

        extra = Extra.forbid

    def embed_documents(self, texts: List[str]) -> List[List[float]]:
        """Compute doc embeddings using a HuggingFace transformer model.

        Args:
            texts: The list of texts to embed.

        Returns:
            List of embeddings, one for each text.
        """
        texts = list(map(lambda x: x.replace("\n", " "), texts))
        embeddings = self.client.encode(texts)
        return embeddings.tolist()

    def embed_query(self, text: str) -> List[float]:
        """Compute query embeddings using a HuggingFace transformer model.

        Args:
            text: The text to embed.

        Returns:
            Embeddings for the text.
        """
        text = text.replace("\n", " ")
        embedding = self.client.encode(text)
        return embedding.tolist()
```

### Usage

```python
embedding_model = HuggingFaceEmbeddings(model_name=model_name, cache_folder=cache_folder)
```

### Motivation


Right now, HuggingFaceEmbeddings doesn't support loading an embedding model's weights from the cache but downloading the weights every time. Fixing this would be a low hanging fruit.

### Your contribution

I can submit a PR if this request makes sense, and I've read `CONTRIBUTING.MD`
This issue should be fixed in `LangChain` sorry for the misreport.