Add isColorLight function

https://github.com/muhammadmuzzammil1998/shiny-octo-doodle/blob/master/JavaScript/isColorLight.js

components/Themes/index.js

@@ -103,6 +103,20 @@ class Themes extends React.PureComponent {
       ...themes
     ]
 
+    let isColorLight = color => {
+      var r, g, b, hsp
+      color = +("0x" + color.slice(1).replace(color.length < 5 && /./g, '$&$&'))
+      r = color >> 16
+      g = color >> 8 & 255
+      b = color & 255;
+      hsp = Math.sqrt(
+        0.299 * (r * r) +
+        0.587 * (g * g) +
+        0.114 * (b * b)
+      )
+      return hsp > 127.5
+    }
+    
     return (
       <div className="themes">
         <Dropdown