add grid, initial version

css/functions/func.scss

@@ -1,3 +1,10 @@
+@mixin inset($top, $right, $bottom, $left) {
+    top: $top;
+    right: $right;
+    bottom: $bottom;
+    left: $left;
+}
+
 @mixin scrollbar() {
     &::-webkit-scrollbar {
         width: 8px;
@@ -8,4 +15,4 @@
         background-color: rgba(168, 168, 168, 0.9);
         border-radius: 4px;
     }
-}
+}