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]

• toolbox

• text editor (property-grid)

• checkbox (property-grid)

• page-navigator

• top-bar: tabbed-menu

• top-bar: buttons (toolbar)

• button-group

• action-button

• data-table (property-grid: matrix-dynamic)

• placeholder (property-grid, waiting for design)

• chapter (property-grid)

• header (property-grid)

• group-caption (property-grid)

• question title (property-grid)

• expression (logic tab?)

• popup

• popup-dropdown
  

• search-editor (property-grid)

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

• notification

• surface

• theme tab

• preview tab

• translation tab

• ...