Theming: Document General Style Changes (PF 6.5) #4952

Detail the broad style changes in PF 6.5's unified theme, addressing updated color palettes, spacing, typography, and any other global adjustments. Include guidance for teams migrating existing products.

Changes that will appear in both PatternFly and Unified themes:

• New Control border token is for improved accessibility

• Subtle borders and shadows on cards

• Accent mark on selected nav items

• New expand/collapse behaviour (up/down)

New Unified theme:

• It leverages the new glass contrast mode by default (see below)

• link to RHDS release notes?

Jira Issue: PF-3680