Tip calculator app

I finally managed to finish this challenge.

It took me a long time to create the js part of the challenge because this was the first calculator challenge I created. I have tested this challenge several times and in different ways to avoid the problem as much as possible (although there may still be some unsolved problems).

The next part of the time was spent on customizing the radio buttons, it wasn't too hard, but it took a while to get the accessibility issue resolved and to be able to work with the calculator using the keyboard buttons (tab and spacebar).

Actually, this is the first challenge where I added "sass build process" to the challenge. which automatically converts the sass code to css by entering the command "npm run build" and then adds all the necessary vendor prefixes to it. Of course, I am a beginner in this new knowledge and I need to spend time improving my knowledge. (I will probably use gulp in the next project).

I am impatiently waiting for your suggestions and criticisms to write better sass and js codes.