CSS Improvements for Landing Page

[joelit]

Description of the enhancement

• [ ] Vocab list category colours need to follow the spec
• [ ] Vocab list link colours need to follow the spec
• [ ] The background should have the line motif
• [x] The background colour should be lighter to follow the spec
• [ ] The UI elements should line up in the bottom of the layout
• [x] The footer should be preceded by a wide margin
• [ ] The space between the columns should be wider