doc: add section on asserting injection context in dependency injection

[SkyZeroZx]

Add section about assertInInjectionContext

[martinboue]

@SkyZeroZx Thank you for your contribution!

I've personally never used assertInInjectionContext before. Besides resolvers or guards, I never use helpers functions that need injection context. That said, I can see the value, especially for library authors.

To make sure this tip is broadly useful and not too niche or advanced (I try to keep Angular Tips accessible), could you please provide a real-world example of a helper function that would benefit from this? Thanks!

[SkyZeroZx]

The most common case, if you have several components or logic that need to access the DOM, is that instead of injecting ElementRef and then NativeElement, it's more practical to have a helper for that, and as you point out, for libraries it's an optimized way.

import { ElementRef, assertInInjectionContext, inject } from '@angular/core';
export function injectNativeElement<T extends Element>(): T {
    assertInInjectionContext(injectNativeElement);
    return inject(ElementRef).nativeElement;
}

[martinboue]

A few minor comments, but nothing major. Thank you for your contribution ❤️

[martinboue]

I took the liberty of changing the order of the two tips and adding the version number to the links to angular.dev, I hope you don't mind.

Thanks again and congrats for being the first PR contributor of Angular Tips! 🎉