remove: improve removal of array items

This commit improves the “remove” action of overlays when targeting an
array element.

Instead of using `delete` on the array item, we remove the item from
the array completely with
[`Array.prototype.splice`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice)
method.

This avoids ending up with `undefined` values in arrays of the
resulting API description.

Author: paulRbr

src/overlay.js

@@ -15,7 +15,11 @@ function applyOverlayToOpenAPI(spec, overlay) {
 				}
 				var parent = jsonpath.parent(spec, a.target)
 				const thingToRemove = path[0][path[0].length - 1]
-				delete parent[thingToRemove]
+				if (Array.isArray(parent)) {
+					parent.splice(thingToRemove, 1);
+				} else {
+					delete parent[thingToRemove];
+				}
 			}
 
 		} else {