[META] OUI Theming Updates

[KrooshalUX]

This issue is a draft/placeholder while OUI team works together on theming system requirements. There is a distinct difference between creating OUI theming capabilities and executing Theme 1. More details to come. Short term:

• [ ] Complete engineering research & approach spike https://github.com/opensearch-project/oui/issues/44
• [ ] Provide a list of themable UI items
• [ ] Identify component-level refactoring to match theming approach

Mid Term:

• [ ] Allow user to set light/dark mode defaults based on system settings

Path to Theme 1 throughout Q1 & Q2:

• [ ] Design exploration of Theme 1 utilizing updated branding colors for light and dark mode
• [ ] End-to-end update of all themeable design assets
• [ ] Replace current OUI base theme with Theme 1
• [ ] Build of Theme 1
• [ ] Version bump of OUI
• [ ] Campaign for OUI version bump adoption

[kavilla]

Update theme default values.

[KrooshalUX]

Update theme default values.

This is "Replace current OUI Base theme with `Theme 1" in the to-do list @kavilla