Determine the minor Angular Version to use this package

See which is the minimal version of Angular to run this directive and update the [`package.json`](https://github.com/bikecoders/ngx-input-search/blob/master/libs/ngx-input-search/package.json#L32-L33) library

We could have e2e testing with different Angular version or investigate what is the best strategy to ensure that the library will work with that Angular version and with recent versions