feat(app-shell): refresh app shell UX

[owilliams320]

Description

Refreshing the app shell experience to support the new TD products branding

What's included?

• CSS updates to appshell and scrolling
• Moving the user-menu slot from the navigation section to above the main area
• Help menu styling improvements
• Styling adjustments to the breadcrumbs in markdown-navigator-component
• Adding a contained property to app shell that wraps the main area in a card styling
• Adding support for a dense property for textfield
• Adding more support to use covalent-icon(s) attribute on the cv-icon component
• Adding support for sticky mode for toolbar
• Exporting missing secondary entry points for some packages

Test Steps

• npm run storybook
• then this open the app shell story
• finally test out the new app shell improvements

General Tests for Every PR

• npm run start still works.
• npm run lint passes.
• npm run stylelint passes.
• npm test passes and code coverage is not lower.
• npm run build still works.

Screenshots or link to StackBlitz/Plunker

[mikespudwebb]

Good stuff!

One comment about redundant imports and one question about borders. But I'm good with them, so

[owilliams320]

🎉 This PR is included in version 8.4.0 🎉

The release is available on:

• v8.4.0
• GitHub release

Your semantic-release bot 📦🚀