Convert to a standard format

[Fcmam5]

Thank you Walid for this useful library!

I have a suggestion for having a method to convert to a standard phone number format, e.g: E.164.

[01walid]

Thank you for pointing this out @Fcmam5 !

I was initially looking if we have a spec/format like some other countries but didn't find any. This looks like a reasonable fallback.

I'll take a look and implement this. You're welcome if you want to contribute of course.