CSS Cleanup and Minor Changes

[TomiZ87]

Acceptance criteria:

• Merge the CSS/SCSS files and styles from masthead and other places to improve modularity.
• Fix small observed bugs
• Change highlighting of links (outside of links in individual blog posts) to be the skip red colour on hover
• Change layout of footer to be the same on desktop and mobile
• Change layout of fallback to default instead of post
• Remove hardcoded breakpoint values
• Add info to CNAME
• Delete unused files