feat: export TransitionOptions interface and getIonPageElement (#28140)

Issue number: resolves #28137

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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.

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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';