addContact method
Add a contact.
Implementation
Future<KeyPairData> addContact(Keyring keyring, Map acc) async {
final pubKey = await (service!.serviceRoot.account
.decodeAddress([acc['address']]));
acc['pubKey'] = pubKey!.keys.toList()[0];
// save keystore to storage
await keyring.store.addContact(acc);
await updatePubKeyAddressMap(keyring);
await updatePubKeyIconsMap(keyring, [acc['pubKey']]);
updateIndicesMap(keyring, [acc['address']]);
return keyring.contacts.firstWhere((e) => e.pubKey == acc['pubKey']);
}