feat(header): add new divider property (#29675)

Issue number: internal

---------

<!-- Please do not submit updates to dependencies unless it fixes an
issue. -->

<!-- Please try to limit your pull request to one type (bugfix, feature,
etc). Submit multiple pull requests if needed. -->

## What is the new behavior?
<!-- Please describe the behavior or changes that are being added by
this PR. -->

- Add new divider property on header's Ionic theme
- Added new divider test.
- Added TODO for support on ios/ md in future.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

<!--
  If this introduces a breaking change:
1. Describe the impact and migration path for existing applications
below.
  2. Update the BREAKING.md file with the breaking change.
3. Add "BREAKING CHANGE: [...]" to the commit description when merging.
See
https://github.com/ionic-team/ionic-framework/blob/main/docs/CONTRIBUTING.md#footer
for more information.
-->


## Other information

<!-- Any other information that is important to this PR such as
screenshots of how the component looks before and after the change. -->

[Header divider
sample](https://ionic-framework-a13vvxiyy-ionic1.vercel.app/src/components/header/test/divider?ionic:theme=ionic)

---------

Co-authored-by: ionitron <hi@ionicframework.com>
Co-authored-by: Giuliana Silva <108938618+OS-giulianasilva@users.noreply.github.com>

packages/angular/src/directives/proxies.ts

@@ -824,14 +824,14 @@ export declare interface IonGrid extends Components.IonGrid {}
 
 
 @ProxyCmp({
-  inputs: ['collapse', 'mode', 'theme', 'translucent']
+  inputs: ['collapse', 'divider', 'mode', 'theme', 'translucent']
 })
 @Component({
   selector: 'ion-header',
   changeDetection: ChangeDetectionStrategy.OnPush,
   template: '<ng-content></ng-content>',
   // eslint-disable-next-line @angular-eslint/no-inputs-metadata-property
-  inputs: ['collapse', 'mode', 'theme', 'translucent'],
+  inputs: ['collapse', 'divider', 'mode', 'theme', 'translucent'],
 })
 export class IonHeader {
   protected el: HTMLElement;