[feat] Create typography and base styles for design system

[markcaron]

We need typography and general base styles for use within the design system. End solution should be a base stylesheet that we can add to our CDN or implementors can include in their sites/apps.

• Discovery CSS solution
• Design: define styles
• Dev: write CSS

Related issues:

• [docs] Update "Typography" page with DPO guidelines #2169

[markcaron]

Discussed in office hours:

• Have multiple CSS files, like reset.css, typography.css, page.css, grid.css, etc.
• Bundle base CSS files in post process on CDN in a separate bundles directory, like rhds-all.css
• Pattern-based styles for lightDOM would exist in rhds/patterns/${pattern-name}/${pattern-name}.css

CSS files could potentially live in rhds/utilities/styles

[markcaron]

Question:
Do we need a tokens.css to act as the interface for the semantic tokens used in typography.css, pages.css, etc.?

Or do we reference the primitive directly?

h1 {
  font-size: var(--rh-font-size-heading-2xl, 3rem);
}

vs

h1 {
  font-size: var(--rh-font-size-h1, var(--rh-font-size-heading-2xl, 3rem));
}