changed the way docs is generated

docs/assets/split.css

@@ -0,0 +1,15 @@
+.gutter {
+    background-color: #f5f5f5;
+    background-repeat: no-repeat;
+    background-position: 50%;
+}
+
+.gutter.gutter-vertical {
+    background-image:  url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAB4AAAAFAQMAAABo7865AAAABlBMVEVHcEzMzMzyAv2sAAAAAXRSTlMAQObYZgAAABBJREFUeF5jOAMEEAIEEFwAn3kMwcB6I2AAAAAASUVORK5CYII=');
+    cursor: ns-resize;
+}
+
+.gutter.gutter-horizontal {
+    background-image:  url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAeCAYAAADkftS9AAAAIklEQVQoU2M4c+bMfxAGAgYYmwGrIIiDjrELjpo5aiZeMwF+yNnOs5KSvgAAAABJRU5ErkJggg==');
+    cursor: ew-resize;
+}