feat: support prefers-color-scheme

[josefaidt]

Support prefers-color-scheme with window.matchMedia() to determine user theme on first visit.

Current Behavior:

on visit, active theme choice is decided by

1. local storage (if exists)
2. fallback to first theme in themes array

Proposed Behavior:

on visit, active theme choice is decided by

1. local storage (if exists)
2. prefers-color-scheme choice (will be light or dark and themes should have a palette with one of these names)
3. fallback to first theme in themes array

Changes

• add new prop to disable proposed behavior, something like disablePrefersColorScheme? Forcing the new behavior may cause unwanted UX adjustments
• add test to prove new behavior and prop are working as intended

[josefaidt]

@dysfunc thoughts on the proposed prop to disable the new behavior?