Create Guidelines section and move pages

[aubrey-oneal]

Depends on #5475

When this issue is finished, the Guidelines section should match the final draft in this IA Figma. This issue is blocked until we have tree nav.

Tasks

• Create a submenu after Patterns called Guidelines
• Create a page called Accessibility. Add content from issue Evaluate Keyboard tabs and Keyboard guidelines pages #5504 , which merges content from Keyboard tabs and Keyboard guidelines and adds additional accessibility guideline.
• Rename the AI design guidance submenu to Artificial intelligence and move the section and its accompanying pages under Guidelines. Requires tree nav.
• Rename the Content guidance submenu to Content and move the section and its accompanying pages under Guidelines. Requires tree nav.
• Move Emails page under Guidelines
• Rename IBM Products layouts to Layouts and move under Guidelines
• Rename Try and buy routes to market to Routes to market and move under Guidelines

[oliviaflory]

This issue was addressed in #5475 and https://github.com/carbon-design-system/carbon-for-products-website/pull/111