feat: export TransitionOptions interface and getIonPageElement (#28140)

Issue number: resolves #28137

---------

Changes according to [this
comment](https://github.com/ionic-team/ionic-framework/issues/28137#issuecomment-1710283096)

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

@liamdebeasi Sorry for replacing the previous PR. I only copied the main
branch to my fork so I couldn't rebase properly. I am unfortunately not
extremely familiar with Github.

---------

Co-authored-by: Philipp Heuer <philipp@studysmarter.de>
Co-authored-by: Liam DeBeasi <liamdebeasi@users.noreply.github.com>

core/src/index.ts

@@ -1,6 +1,7 @@
 import 'ionicons';
 
 export { createAnimation } from './utils/animation/animation';
+export { getIonPageElement } from './utils/transition';
 export { iosTransitionAnimation } from './utils/transition/ios.transition';
 export { mdTransitionAnimation } from './utils/transition/md.transition';
 export { getTimeGivenProgression } from './utils/animation/cubic-bezier';

core/src/interface.d.ts

@@ -43,6 +43,7 @@ export {
   AnimationKeyFrames,
   AnimationLifecycle,
 } from './utils/animation/animation-interface';
+export { TransitionOptions } from './utils/transition';
 export { HTMLIonOverlayElement, OverlayController, OverlayInterface } from './utils/overlays-interface';
 export { Config, config } from './global/config';
 export { Gesture, GestureConfig, GestureDetail } from './utils/gesture';