Add support to expand existing shortcuts with new ones rather than having to rewrite them all from scratch

[zubozrout]

The default set of shortcuts present in the list is good, but it would be great if it could be expanded rather than simply overwritten with a custom set of options: https://github.com/elreco/vue-tailwind-datepicker/blob/8a9c63b4372e8bbe42b525f76c2243ab02b135e6/src/components/Shortcut.vue#L47

Would it be feasible to expand the date range picker with a property allowing the custom shortcuts to rather get appended to the list? Or for the flexibility perhaps it could be two new lists like prepend-shortcuts and append-shortcuts, not sure.

Thank you so much.

[mrspartak]

+1 on this

[tiYusupov]

+1 !