feat: add support for custom placeholder template

[numandev1]

Summary:

#1470 we need to add the custom placeholder flags while init. so i added this custom placeholder support in cli

Test Plan:

you can download this template and test by this command https://github.com/nomi9995/react-native-template-placeholder

react-native init test --template file:///Users/apple/clitest/react-native-template-placeholder 

[gabrieldonadel]

@nomi9995 seems that tests are failing, do you mind taking a look?

[numandev1]

@gabrieldonadel this is an architectural change so we have to update test cases if it is functionality-wise okay then i will also write test cases.

[github-actions[bot]]

There hasn't been any activity on this pull request in the past 3 months, so it has been marked as stale and it will be closed automatically if no further activity occurs in the next 7 days.