Create theme-unaware high-level tokens

🙋 Feature Request

😯 Problem to Solve

We currently have:

• theme-unaware base tokens such as $ni-nimble-base-black-85 that are static values defined as raw values
• theme-aware high-level tokens such as $ni-nimble-application-background-color that are dynamic values that change at runtime based on JavaScript, the nimble-theme-provider custom element, and programmatically updating CSS Custom Property values

We should consider having:

• theme-unaware high-level tokens such as $ni-nimble-application-background-color-light-theme, $ni-nimble-application-background-color-dark-theme, $ni-nimble-application-background-color-color-theme that are static values defined as raw values
• we should then build the theme-aware high-level tokens from those theme-unaware high-level tokens

Use-cases:

• Mobiscroll does not support theming using dynamic CSS custom properties and needs statically defined SCSS values (discussion)
• Gainsights does not support JavaScript execution which is needed for our theme-aware high-level tokens to update dynamically. We could instead generate static CSS styles that use prefers-color-scheme to have top-level page system theme awareness (but no concept of theme-providers to override themes on specific regions of a page dynamically).

💁 Proposed Solution

Partially described above but we need to determine:

• The naming scheme for theme unaware high-level tokens
• How to represent the theme-unaware high-level tokens in style dictionary
• Generation of static CSS that uses the prefers-color-scheme media query (current use-case being gainsights so should see what is actually supported first)

📋 Tasks

Start by reviewing the existing theme-unaware base tokens and theme-aware high-level tokens, plus the Style Dictionary representation described in the issue. Define the naming and representation for theme-unaware high-level tokens, then verify whether static CSS generation with prefers-color-scheme is supported for the Gainsights use case and document the resulting approach.