Added colors and designs, fixed bugs, and improved UI

Kawaii Windows March Update 

Hello! This might be the last update I will make for this project since there's pretty much nothing else to do with it. So, here is the list of the changes I have made:

• Added more theme colors (purple, sunset, avocado)
• Added styles (D, E)
• Collapsible menu for tablets and desktop
• Changed "Kawaii Windows Generator" to "Kawaii Popup Window Generator"

I know it's not much, but I hope it improves your experience. I will also be migrating this tool to my own website soon. Good day everyone!