Resolve "Create Basic HTML Structure"

All separate actions were made as commits. Would appreciate a review 😄

In short, actions made:

• Deleted leftover JS code;
• Added text on register.html to redirect to login.html as currently is on the latter;
• Moved CSS from register.html, login.html into login.css. Created CSS for index.html in main.css
• Created initial version of the dashboard.

Would love to hear your thoughts on the layout of the dashboard. Let me know if any other elements should be added or the layout should be changed.

Closes #1 (closed)