Change function result type from string to any

Updated the return type of functions and related code from `string` to `any` to improve flexibility and support more diverse outputs. Adjusted function implementations, signatures, and handling of results accordingly.

functions.go

@@ -1,8 +1,9 @@
 package go_llm
 
 import (
-	"gitea.stevedudenhoeffer.com/steve/go-llm/schema"
 	"reflect"
+
+	"gitea.stevedudenhoeffer.com/steve/go-llm/schema"
 )
 
 // Parse takes a function pointer and returns a function object.
@@ -12,7 +13,7 @@ import (
 // The struct parameters can have the following tags:
 // - Description: a string that describes the parameter, passed to openaiImpl to tell it what the parameter is for
 
-func NewFunction[T any](name string, description string, fn func(*Context, T) (string, error)) *Function {
+func NewFunction[T any](name string, description string, fn func(*Context, T) (any, error)) *Function {
 	var o T
 
 	res := Function{