How to open calendar from other button

https://github.com/fetrarij/ngx-daterangepicker-material/pull/47#issue-220117180

For all element we want to allow an action to the calendar (show, hide,...)

1. add the class ngx-daterangepicker-action to the element
2. use ViewChild or ViewChildren to access all method in DaterangepickerDirective or DaterangepickerComponent.

See demo code on: demo/src/app/simple