feat: add dashscope(alibabacloud) as new provider to gateway

[heimanba]

Title: add dashscope(alibabacloud) as new provider to gateway
DashScope is an AI solution provided by Alibaba Cloud. And is already compatible with the OpenAI interface, as mentioned here: https://help.aliyun.com/zh/model-studio/developer-reference/compatibility-of-openai-with-dashscope

Motivation: (optional)

• Using gateway to call DashScope's AI large model

Related Issues: (optional)

• #662

[narengogi]

LGTM, though I'm not able to verify this in my local (I have no way of signing up for an account on https://account.aliyun.com/register/qr_register.htm?oauth_callback=https%3A%2F%2Fdashscope.aliyun.com%2F )

[heimanba]

LGTM, though I'm not able to verify this in my local (I have no way of signing up for an account on https://account.aliyun.com/register/qr_register.htm?oauth_callback=https%3A%2F%2Fdashscope.aliyun.com%2F )

test case

import { Portkey } from 'portkey-ai';

const portkey = new Portkey({
    apiKey: "ANTHROPIC_API_KEY",
		baseURL: "http://127.0.0.1:8787/v1",
		config:{
			model: "qwen-plus",
			"provider": "dashscope",
			api_key: "sk-xxx",
		}
});

const completion = await portkey.chat.completions.create({
	messages: [
			{ role: "system", content: "You are a helpful assistant." },
			{
					role: "user",
					content: "wo are you？",
			},
	],
});
console.log(completion.choices[0].message);