Update isWeekday.md

We should probably make this and the isWeekend snippet have the same description...

snippets/isWeekday.md

@@ -3,11 +3,11 @@
 Results in a boolean representation of a specific date.
 
 Pass the specific date object firstly.
-Use `Date.getDay()` to check weekday then return a boolean.
+Use `Date.getDay()` to check weekday by using a modulo operator as then returning a boolean.
 
 ```js
 const isWeekday = (t = new Date()) => {
-  return t.getDay() >= 1 && t.getDay() <= 5;
+  return t.getDay() % 6 !== 0;
 };
 ```