Add 'main-container' section with aside and content sections.
Add base styles to body.
Add base styles to header.
Change 'main-container' class to 'content'. Change 'content' class to 'main'.
Add base styles to content section.
Add base structure of typography section.
Remove 'heading' and 'sub-heading' classes from structure.
Add class 'topic' to introduction and typography sections.
Add margin-bottom to 'topic' sections.
Add base styles to 'example' blocks.
Add 'caption' to typography examples list.
Add base structure for 'Colors' section.
Add base styles to 'swatch-list' and swatches.
Update example paragraph copy on typography section.
Remove 'caption' example from typography section.