feat: add ability to pick multiple contacts

[Chronos77]

Describe the solution you'd like
You should do like the pickContact but to select several contacts

[tafelnl]

I will only implement this if iOS and Android support this natively out of the box. The reason for this is that it will be very hard to maintain otherwise. Every user's requirements are different, and it will be impossible to account for them all.

I know that both iOS and Android support a single contact picker. That's why it's implemented in this plugin.

It looks like that iOS might support a multi picker as well. However I cannot seem to find anything similar for Android. Are you aware of any such feature?

[tafelnl]

A few related SO questions after a quick search:

https://stackoverflow.com/questions/33289587/contact-intent-with-multiple-select/35505683

https://stackoverflow.com/questions/59307787/how-to-enable-multiple-selection-from-contact-list

https://stackoverflow.com/questions/21200437/select-multiple-contacts-from-phone-book-in-android