New theme setting
[ ] "Sync with OS appearance settings"
Functional notes in the Figma design file below
Things to consider
Existing themes will need to now be defined as light or dark in the theme definition somehow
Due to above, ensure there are no breaking changes for users using existing themes
How do we migrate custom themes?
What limitations might there be for Windows/Android? Which version of the OS supports this and therefore which should we set the default to TRUE for?
Other things to consider
custom theme generator: https://avasconcelos114.github.io/mattermost-themes/
already has light and dark themes categorized