Document best practices for handling modal life cycle events with frameworks

**URL**
The URL at which the content is missing or inaccurate: https://ionicframework.com/docs/api/modal

**What is missing or inaccurate about the content on this page?**

We should document best practices with life cycle events for `ion-modal` and frameworks. Since it is a common pattern to present the modal from code external to a component, for example in Angular within a service; developers will need to be instructed on how to best listen and respond for when the modal is presented from their component.

For Angular, it makes the most sense to use rxjs subjects to emit changes after the modal is presented.

Reference issue: https://github.com/ionic-team/ionic-framework/issues/25250