shorten day of week format for English

Author: AaronThornton00

src/js/rangedate-picker.js

@@ -10,7 +10,7 @@ const availableMonths = {
 }
 
 const availableShortDays = {
-  EN: ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'],
+  EN: ['Su', 'Mo', 'Tu', 'We', 'Th', 'Fr', 'Sa'],
   ID: ['Min', 'Sen', 'Sel', 'Rab', 'Kam', 'Jum', 'Sab']
 }