Link to MDN instead of WHATWG spec [ci-skip]

MDN provides a more accessible explanation.

Author: jonathanhefner

guides/source/configuring.md

@@ -2411,7 +2411,7 @@ The default value depends on the `config.load_defaults` target version:
 
 #### `config.action_view.image_loading`
 
-Specifies a default value for the `loading` attribute of `<img>` tags rendered by the `image_tag` helper. For example, when set to `"lazy"`, `<img>` tags rendered by `image_tag` will include `loading="lazy"`, which [instructs the browser to wait until an image is near the viewport to load it](https://html.spec.whatwg.org/#lazy-loading-attributes). (This value can still be overridden per image by passing e.g. `loading: "eager"` to `image_tag`.) Defaults to `nil`.
+Specifies a default value for the `loading` attribute of `<img>` tags rendered by the `image_tag` helper. For example, when set to `"lazy"`, `<img>` tags rendered by `image_tag` will include `loading="lazy"`, which [instructs the browser to wait until an image is near the viewport to load it](https://developer.mozilla.org/en-US/docs/Web/API/HTMLImageElement/loading#lazy). (This value can still be overridden per image by passing e.g. `loading: "eager"` to `image_tag`.) Defaults to `nil`.
 
 #### `config.action_view.image_decoding`