Update stale doc strings

[taranjeet]

In embedchain/embedchain.py, there are some doc strings which have become stale. Eg

class App(EmbedChain):
    """
    The EmbedChain app.
    Has two functions: add and query.

    adds(data_type, url): adds the data from the given URL to the vector db.
    query(query): finds answer to the given query using vector database and LLM.
    dry_run(query): test your prompt without consuming tokens.
    """

This issue is about going through all the doc strings in this file and updating/improving all the doc strings.

[rajveer43]

would like to work on this