chore: add angular 21 documentation

Author: AtofStryker

docs/app/component-testing/angular/examples.mdx

@@ -157,6 +157,24 @@ it('clicking + fires a change event with the incremented value', () => {
 })
 ```
 
+### Working with Legacy @Input() Decorators
+
+With the release of Angular 18, [signals](https://angular.dev/guide/signals) became the preferred way to handle data binding. 
+However, legacy components that use `@Input()` and `@Output()` decorators are still supported.
+
+Interacting with legacy `@Input()` decorators is a bit different than working with signals.
+In order to update the `@Input()` value, you need to use the `componentRef.setInput` method so Angular change detection runs properly.
+Otherwise, you may see errors.
+
+```ts
+cy.mount(StepperComponent, { componentProperties: { count: 100 } }).then(({ fixture }) => {
+  return cy.contains('span', '100').wrap(fixture)
+}).then((fixture) => {
+  fixture.componentRef.setInput('count', 110)
+  return cy.contains('span', '110')
+})
+```
+
 ### Using createOutputSpy()
 
 To make spying on event emitters easier, there is a utility function called

docs/app/component-testing/angular/overview.mdx

@@ -20,7 +20,7 @@ sidebar_label: Overview
 
 ## Framework Support
 
-Cypress Component Testing supports Angular `^18.0.0`, `^19.0.0`, and `^20.0.0`.
+Cypress Component Testing supports Angular `^18.0.0`, `^19.0.0`, `^20.0.0`, and `^21.0.0`.
 
 :::info
 

docs/app/component-testing/get-started.mdx

@@ -47,7 +47,7 @@ following development servers and frameworks:
 | [Next.js 14-16](/app/component-testing/react/overview#Nextjs)                                                      | React 18-19   | Webpack 5 |
 | [Vue with Vite](/app/component-testing/vue/overview#Vue-with-Vite)                                                 | Vue 3         | Vite 5-7  |
 | [Vue with Webpack](/app/component-testing/vue/overview#Vue-with-Webpack)                                           | Vue 3         | Webpack 5 |
-| [Angular](/app/component-testing/angular/overview#Framework-Configuration)                                         | Angular 18-20 | Webpack 5 |
+| [Angular](/app/component-testing/angular/overview#Framework-Configuration)                                         | Angular 18-21 | Webpack 5 |
 | [Svelte with Vite](/app/component-testing/svelte/overview#Svelte-with-Vite) <Badge type="info">Alpha</Badge>       | Svelte 5      | Vite 5-7  |
 | [Svelte with Webpack](/app/component-testing/svelte/overview#Svelte-with-Webpack) <Badge type="info">Alpha</Badge> | Svelte 5      | Webpack 5 |