Improve accessibility of navigation bar and footer (#22635)

Added ARIA navigation landmark to navigation bar and aria label for both
nav bar and footer.

Contributed by @forgejo.

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

options/locale/locale_en-US.ini

@@ -111,6 +111,12 @@ never = Never
 
 rss_feed = RSS Feed
 
+[aria]
+navbar = Navigation Bar
+footer = Footer
+footer.software = About Software
+footer.links = Links
+
 [filter]
 string.asc = A - Z
 string.desc = Z - A