create a simple interactive webpage that changes the background color based on user input.

The HTML file contains a color picker input and a button. When the user selects a color using the color picker and clicks the button, we want the background color of the webpage to change accordingly.

In the JavaScript file, we have a function changeBackgroundColor(). This function is called when the button is clicked.

When the button is clicked, the background color of the webpage will change to the color selected by the user in the color picker.