Added preloader to hide elements before they are correctly rendered

src/web/stylesheets/themes/_classic.scss

@@ -72,6 +72,14 @@ $argBackground: #fff;
 $argDisabledBackground: #eee;
 
 
+// Highlighter colours
+$hl1: #fff000;
+$hl2: #95dfff;
+$hl3: #ffb6b6;
+$hl4: #fcf8e3;
+$hl5: #8de768;
+
+
 // Misc.
 $dropFileBorderColour: #3a87ad;
 
@@ -81,10 +89,3 @@ $bannerBgColour: #dff0d8;
 $scrollbarTrack: $secondaryBackgroundColour;
 $scrollbarThumb: #ccc;
 $scrollbarHover: #bbb;
-
-// Highlighter colours
-$hl1: #fff000;
-$hl2: #95dfff;
-$hl3: #ffb6b6;
-$hl4: #fcf8e3;
-$hl5: #8de768;