[FR] UI Full Customization

### Description

Have premade themes as choice selection is tacky & dull to follow the typical motto. As an open source alternative people like to customize their own UI with workspaces so lets make it happen. Rewrite appearance to be a CSS selector so a person can select their own colors for the UI from a color picker or input by color code.

### Impact

Makes people happy to have a nortion alternative where they can customize their own UI. I like mine black and red maybe you like yours terminal green theme or perhaps you like purple and yellow together.

### Additional Context

Make it happen!