Implement From<serde_json::Error> on OpenAIError enum

[ozaner]

The OpenAIError type is implemented using the thiserror crate. It implements From<reqwest::Error> via the #[from] present in the Reqwest variant.

async-openai/async-openai/src/error.rs

Lines 4 to 28 in c48e62e

	#[derive(Debug, thiserror::Error)]
	pub enum OpenAIError {
	/// Underlying error from reqwest library after an API call was made
	#[error("http error: {0}")]
	Reqwest(#[from] reqwest::Error),
	/// OpenAI returns error object with details of API call failure
	#[error("{0}")]
	ApiError(ApiError),
	/// Error when a response cannot be deserialized into a Rust type
	#[error("failed to deserialize api response: {0}")]
	JSONDeserialize(serde_json::Error),
	/// Error on the client side when saving file to file system
	#[error("failed to save file: {0}")]
	FileSaveError(String),
	/// Error on the client side when reading file from file system
	#[error("failed to read file: {0}")]
	FileReadError(String),
	/// Error on SSE streaming
	#[error("stream failed: {0}")]
	StreamError(String),
	/// Error from client side validation
	/// or when builder fails to build request before making API call
	#[error("invalid args: {0}")]
	InvalidArgument(String),
	}

I think that the #[from] attribute should also be present for the JSONDeserialize variant as well.

Having From<serde_json::Error> implemented would allow me to use it as a trait bound for the error type of my own custom Llm trait.

This is addressed by PR #325