Add overlay to the new theme

static/overlay.less

@@ -3,14 +3,11 @@
   left: 50%;
   width: 500px;
   margin-left: -250px;
-  background: #202123;
-  color: #eee;
-  padding: 10px;
   z-index: 9999;
   box-sizing: border-box;
-  border: 1px solid rgba(255, 255, 255, 0.05);
-  box-shadow: 0 0 10px rgba(0, 0, 0, 0.5);
-  border-radius: 3px;
+
+  background-color: #fff;
+  padding: 10px;
 }
 
 .overlay .editor.mini {

themes/neue-dark-ui/overlay.less

@@ -0,0 +1,14 @@
+@import "ui-variables";
+
+.overlay {
+  color: @text-color;
+  background-color: @overlay-background-color;
+  padding: @component-padding;
+  border: 1px solid @overlay-border-color;
+  box-shadow: 0 0 10px @overlay-shadow-color;
+  border-radius: @component-border-radius;
+}
+
+.overlay .editor.mini {
+  margin-bottom: @component-padding;
+}

themes/neue-dark-ui/package.cson

@@ -8,4 +8,5 @@
   'lists'
   'editor'
   'tabs'
+  'overlay'
 ]

themes/neue-dark-ui/ui-variables.less

@@ -32,6 +32,10 @@
 
 @panel-heading-background-color: #43484d;
 
+@overlay-background-color: #202123;
+@overlay-border-color: rgba(255, 255, 255, 0.05);
+@overlay-shadow-color: rgba(0, 0, 0, 0.5);
+
 @button-color: #303030;
 @button-color-hover: #353536;
 @button-color-active: #404040;