Add claude sonnet 3.5 support

[VersaceXcodes]

Hi, can we have claude sonnet 3.5 added to the llms lagent? thanks

[Harold-lkk]

"We are currently restructuring the LLM, so the support may be slower. If you just want to call some Claude, you only need to modify the base URL of the GPTAPI and change the way you extract the output."