[arabic/urdu] Add example of date separator

[r12a]

Comment on http://r12a.github.io/scripts/arabic/urdu

(and fix the autogeneration of the link above)

See

Here's the example: ۲؍صفر۲۰۳۱؁ھ

Works with Awami Nastaliq, however there's also a couple of issues:

1. sanah should in principle be before, not after, the numbers
2. sanah only works if bidi override is applied - not sure why