Re-design Pull Request

[SerjSX]

Hello, I wanted to volunteer in re-designing the website to one that's more modern and easy to look at.

These are the changes done:

1. Background color changed to a dark one (I can easily add a dark mode toggle instead with the option to toggle the theme, if needed)
2. Changed the theme of the "Sections" AKA "Table of Content"
3. Change the design of the normal information part (news, versions, description...)
4. Changed the background color of the Manual page so it would match with the normal pages
5. Added a "Back" button at the top of the first Manual page so you would go back to the main page of the normal website
6. Cleaned the code, removed W3school stuff (I think that was being used) and made a separate folder for CSS files. HTML and CSS are separate, easier to edit and navigate.
7. Buttons and clickable images (the logo) have effects, as in on hover.
8. Very small, with a light font and color, watermark that I re-designed the website. OF COURSE this is optional and you can remove it.
9. Organized the HTML files with divs and so on, they were normal with which makes the HTML file messy. Now everything is organized.

What I didn't do:

1. I didn't touch to any of the other files, as in media and etc.
2. I didn't touch to the API Reference websites since they are important, so I kept it the same way.
3. I didn't change the texts of any of the contents inside the sites other than the news versions, I removed the repetitive "Qalculate!". Of course you can add it anytime.

I hope you enjoy it!! This was pure volunteering.