Bug 1701987 - Add comment and access key to "Location" label, r=Gijs,fluent-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D110280

browser/locales/en-US/browser/editBookmarkOverlay.ftl

@@ -10,8 +10,11 @@ bookmark-overlay-url =
   .value = URL
   .accesskey = U
 
+# Location refers to the position of the bookmark within the browser's
+# bookmarks, not to its URL or address.
 bookmark-overlay-location-2 =
   .value = Location
+  .accesskey = L
 
 bookmark-overlay-choose =
   .label = Choose…