Fix CORS compatibility with OpenAI, vLLM, TGI, LMDeploy

[josephrocca]

Motivation

Fixes #333

Fix CORS compatibility with OpenAI API, vLLM, TGI, LMDeploy, TabbyAPI, and others. Currently SGLang is the only one which does not use wildcard CORS headers. This makes it annoying to make requests directly from a web page to a SGLang server, since it requires adding an extra proxy server in between to add the CORS headers.

My particular use case is an in-browser eval framework. An intermediary server is not needed for this use case, except to solve this CORS issue.

Examples:

• https://github.com/vllm-project/vllm/blob/da1a844e61366b473cef6b3f7437ea5dc41876a1/vllm/entrypoints/openai/api_server.py#L389
• https://github.com/InternLM/lmdeploy/blob/e8a1a33aa826646420ed2e67250d8eb97cf5cea9/lmdeploy/serve/proxy/proxy.py#L306

Modifications

Add CORS middleware.

[zhyncs]

Hi @josephrocca Long time no see! Didn't expect to find you here in SGLang again. Glad to see you using SGLang. Feel free to join our Slack channel at https://sgl-fru7574.slack.com/join/shared_invite/zt-2ngly9muu-t37XiH87qvD~6rVBTkTEHw

[zhyncs]

@josephrocca Please follow https://github.com/sgl-project/sglang/blob/main/docs/en/contributor_guide.md to resolve the lint issue. Thanks!

[zhyncs]

Hi @josephrocca I have directly resolved some format issues based on your work, and it has been merged. Thank you very much for your contribution!

[josephrocca]

Thanks!