adds the ability to run example app tests against d14n testnet staging#774

cameronvoell wants to merge 3 commits intomainxmtp/xmtp-react-native:mainfrom

cv/03-13-adds_the_ability_to_run_example_app_tests_against_d14n_testnet_stagingxmtp/xmtp-react-native:cv/03-13-adds_the_ability_to_run_example_app_tests_against_d14n_testnet_stagingCopy head branch name to clipboard