Use description and title front matter for pages rendered from /content

[alex-page]

This PR:

• Removes all # title from markdown and uses title from frontmatter
• Moves the first paragraph of markdown files to description in frontmatter
• Updates all pages to use the frontmatter correctly

Follow ups:

• Remove custom styling for descriptions
• Consolidate repetitive markdown page elements
• Remove components.json, foundations.json and navbar generation - replace with frontmatter