feat: export DEFAULT_COUNTRIES from defaultCountriesData (#320)

[samMeow]

resolve #320
expose DEFAULT_COUNTRIES from components/AllCountries

Description

export DEFAULT_COUNTRIES from defaultCountriesData in components/AllCountries

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have used ESLint & Prettier to follow the code style of this project.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.