added 'back to main menu' button index.js

[JordanDickow]

I love the game! It needs a button that leads users back to the main menu.
I added another section and the button itself needs to show up after the player starts the game.

[HarishTeens]

Thanks for showing your interest @JordanDickow , The button is not visible in the index.ejs since you have it has the res-btn class,
if you want to add the Back to Main button, add it in all pages as well , and place it on the top so that it would be accessible