prop(lomiri-default-settings): investigate viability of custom `lomiri-ui-toolkit` theme

[oklopfer]

May be possible for us to have RL colors rather than plain dark for Lomiri ui based on:
https://gitlab.com/ubports/development/core/lomiri-ui-toolkit/-/blob/main/src/imports/Components/1.3/LomiriColors.qml

https://gitlab.com/ubports/development/core/lomiri-ui-toolkit/-/tree/main/src/imports/Components/Themes/SuruDark