feat: Update index.jsp (#3066)

Title: Added a <title> element to provide a title for the page.
Enhanced Styling: Improved styling for readability and aesthetic appeal, including a background color and box shadow for the parameter section.
Expanded Descriptions: Clarified the purpose of each parameter.
Example Request: Provided an example of how to format a GET request.
Error Handling Tip: Included a note on what to do if the request fails.