fix: layout css, fixed docsifyjs#409

Author: QingWei-Li

src/themes/basic/_layout.styl

@@ -388,7 +388,7 @@ body.sticky
 
 body.close
   .sidebar
-    transform translateX(-$sidebar-width)
+    transform translateX(- $sidebar-width)
 
   .sidebar-toggle
     width auto
@@ -415,7 +415,7 @@ body.close
     overflow-x hidden
 
   .sidebar
-    left -$sidebar-width
+    left - $sidebar-width
     transition transform 250ms ease-out
 
   .content