Implement themes for SurveyJS Creator

[tsv2013]

• [ ] light restyling #5135
• [ ] sevral themes (including high contrast)
• [ ] UI for theme selection
• [ ] #3652
• [ ] #3754

[mikeamelin]

Components — https://www.figma.com/file/i6Lpc7zkjHtso2oXZV97fo/*-Components?type=design&node-id=2046-19865&mode=dev

Variables.zip

[dmitry-kurmanov]

• [x] toolbox

• [x] text editor (property-grid)

• [x] checkbox (property-grid)

• [x] page-navigator

• [x] top-bar: tabbed-menu

• [x] top-bar: buttons (toolbar)

• [x] button-group

• [x] action-button

• [x] data-table (property-grid: matrix-dynamic)

• [x] placeholder (property-grid, waiting for design)

• [x] chapter (property-grid)

• [x] header (property-grid)

• [x] group-caption (property-grid)

• [x] question title (property-grid)

• [x] expression (logic tab?)

• [x] popup

• [x] popup-dropdown

• [x] search-editor (property-grid)

• [x] search-result highlighting (.spg-editor--highlighted, waiting for design)

• [x] notification

• [x] surface

• [x] theme tab

• [x] preview tab

• [x] translation tab

• [ ] ...