Support Custom Endpoint for Anthropic Provider

[chatGPTxx]

Describe the need of your request

My company has our own proxy API endpoint to redirect Anthropic request.
Current Anthropic Provider doesn't allow user to specific custom base URL as "Custom OpenAI"

Proposed solution

Could you please add a "Custom URL" input box below the "API key", "API version" and "Model" input boxes?
So that the Claude model chats will be sent to the "Custom URL" instead of Anthropic.
Thanks!

Additional context

No response