Fix scaled font blurriness in context menus (#400)

Requires that fonts scale in increments of 0.25.

src/ContextMenu.ts

@@ -194,7 +194,7 @@ export class ContextMenu {
     root.style.left = left + "px"
     root.style.top = top + "px"
 
-    if (options.scale) root.style.transform = `scale(${options.scale})`
+    if (options.scale) root.style.transform = `scale(${Math.round(options.scale * 4) * 0.25})`
   }
 
   addItem(