Update article.md

Changed spelling of "neighbor" from British ("neighbour") to American.

I think that's how you want it. Otherwise some other stuff has to be switched to British.

Author: paroche

2-ui/1-document/03-dom-navigation/article.md

@@ -226,7 +226,7 @@ The links are similar to those given above, just with `Element` word inside:
 
 - `children` -- only those children that are element nodes.
 - `firstElementChild`, `lastElementChild` -- first and last element children.
-- `previousElementSibling`, `nextElementSibling` -- neighbour elements.
+- `previousElementSibling`, `nextElementSibling` -- neighbor elements.
 - `parentElement` -- parent element.
 
 ````smart header="Why `parentElement`? Can the parent be *not* an element?"
@@ -323,7 +323,7 @@ There are also additional navigation properties for HTML forms. We'll look at th
 
 ## Summary
 
-Given a DOM node, we can go to its immediate neighbours using navigation properties.
+Given a DOM node, we can go to its immediate neighbors using navigation properties.
 
 There are two main sets of them: