feat(theme): customTheme-Default im State + Reset-Literal

src/js/settings.js

@@ -550,7 +550,7 @@ function bindSettingsEvents() {
     settings = { compact: false, shortenTitles: false, newTab: true, showDesc: false,
                  hideExtra: false, visibleCount: 10, bgUrl: '', theme: 'nebula',
                  showSearch: true, searchEngine: 'google', toolbarPos: 'right',
-                 imageRefEnabled: false, language: 'auto' };
+                 imageRefEnabled: false, language: 'auto', customTheme: null };
     await saveBoards();
     await saveTrash();
     await saveSettings();

src/js/state.js

@@ -25,6 +25,7 @@ let settings = {
   visibleCount:  10,
   bgUrl:         '',
   theme:         'nebula',
+  customTheme:   null,
   showSearch:    true,
   searchEngine:  'google',
   toolbarPos:    'right',