Prepare 7.0.0 release

[aduth]

7.0.0

Breaking Changes

• NPM package renamed from identity-style-guide to @18f/identity-design-system. (#331)
• Update USWDS from 2.13.3 to 3.4.1. (#321)
• Polyfills have been removed, consistent with current Login.gov browser support
• The following JavaScript named exports have been renamed or removed:
  • navigation is renamed to header
  • validator is renamed to validation
• Refer to README.md for updated usage instructions, as well as the U.S. Web Design System migration guide.
• Sass artifacts now require Dart Sass. The Ruby Sass and LibSass (C) compilers are no longer supported. (#298)
• To improve performance of the default CSS bundle, responsive utility breakpoints other than tablet: have been disabled by default. Previously, mobile-lg: and desktop: utilities were also enabled. You can restore the >original settings by overriding the $theme-utility-breakpoints Sass variable. (#298)
  • Component styling which previously responded to now-disabled breakpoints have been updated to standardize on the tablet breakpoint. This affects usa-button--wide, usa-search--big, and usa-intro CSS classes.
• Image URLs in stylesheets are no longer processed by asset-path-if-exists. For Rails integrations, consider using the $theme-image-path Sass variable in combination with Sprockets resolve_assets_in_css_urls option. (#298)
• The deprecated $image-path Sass variable setting has been removed. Use $theme-image-path instead. (#298)
• The deprecated alerts/success-badge.svg image has been removed. Use alerts/success.svg instead. (#298)
• The deprecated .usa-form-hint CSS class has been removed. Use .usa-hint instead. (#337)
• Removed usa-alert__paragraph alert helper class. Use measure-3 measure utility instead. (#298)
• The Spinner component has been removed (.lg-spinner). A new "Loading" component will be made available in a future release. (#347)

New Features

• Add Tag component styles. (#346)

[zachmargolis]

LGTM