Add link to "Dependency Injection Like Bevy From Scratch" to the Next Steps learning resources

Very useful for understanding (conceptually) how the ECS works, which is a common follow-up question for beginners.

The idea would be to place it in here: https://bevyengine.org/learn/book/next-steps/

Link: https://promethia-27.github.io/dependency_injection_like_bevy_from_scratch/introductions.html

@PROMETHIA-27, are you cool with this?

Open the Next Steps learning resources page and inspect the website source that renders it; start by finding the existing resource links. Done means the page includes the “Dependency Injection Like Bevy From Scratch” title, points to the referenced URL, and displays correctly.

Written by the indexing model from the issue text.