Added a close button as a UX improvement

[frazras]

I created a close_button configuration and close button, all were done in js code.

[flouthoc]

@frazras it looks great 👍 but uglipop was supposed to be minimal , close button can be manually added by user as per their need , but you can add close button as uglipop plugin , i can create a uglipop plugin directory and you can add close button plugin there , so i'm creating a plugin directory you can add your js file there with description about thing your plugin does and a small text about author info , so i'll create directory plugins and you can make a pull like this plugins/closeButton/close.js you can add the exact same js file there , which will be uglipop+close button 😄

[flouthoc]

@frazras Would you like to take a look at conflict ? and re-create this PR

[flouthoc]

Please add these changes on updated js file to resolve conflicts.