Readme is modified (#10)

* package description is modified

* generating function list details are added to readme

* indentation is fixed in readme

* indentation is fixed in readme

* indentation is fixed in readme

* indentation is fixed in readme

* readme is improved

* Define Function Signature Mapping section is added to readme

* Define Function Signature Mapping header reference is added related parts

* function_signature_mapping position is moved up in config section

* Schemas, preparePromptFunctionPayload and prepareFunctionResultsPayload are added to readme

* Generate Prompt Function Instructions is added to readme

* Generate Prompt Function Instructions reference is added to readme

* Send Tool Use (Function Calling) Request to OpenRouter and Validate Function Signature added to readme

* indentation is fixed

* table of contents is modified

* Quick Usage Guide is added to readme

* indentation is fixed

* Table of Contents is fixed

* Table of Contents is fixed

* line separation is added in readme for Quick Usage Guide

* indentation fixes in readme