Minor accessibility issue

[davidmcdermott2]

Steps to produce issue

1. Ensure your Android device supports Talkback (screen reader) and turn it on
2. Ensure the CountryCodePicker has a country preference set
3. Open the CountryCodePicker dialog and scroll through the list of countries
4. The horizontal divider line will be read as "unlabeled" by Talkback without these changes which would be confusing to users
5. With this PR the divider will be read as "country preference divider" instead

It's possible to set the divider as skippable by Talkback but this requires bumping min sdk from 14 to 16

[darcishED]

Why are making the default preferences to US?.. can't the user of the library choose the preference he/she wants?

otherwise, everything else LGTM.

[davidmcdermott2]

Hello I have removed the default US preference. No reason for it. Thank you