[FEATURE]Support Custom API Endpoint Configuration

[amojury]

Is your feature request related to a problem? Please describe.
I would like to request the ability to configure a custom API endpoint in the prompt-explorer tool, rather than relying solely on the default OpenAI API endpoint.
Describe the solution you'd like
Add an option in the configuration to specify a custom API endpoint.

Thank you for considering this request!

[mkagit]

Custom endpoint URL would be great as for today you can use a lot of free or very cheap LLMs OpenAI endpoint compatible.