Support older browsers that lack Intl
Support older browsers that lack Intl

While Intl.NumberFormat is a much more performant implementation
(see #1566), and is supported by all modern browsers, there are
still older browsers in the wild that lack support for it. Most
notably, Safari 9 and the Android built-in browser do not support
it, leaving many users stuck on older iPads and Macs unable to
access the site.

By checking for Intl support before using it, we ensure backwards
compatibility, while also using the more performant modern options
wherever available.

Refs #1804 :bug: :apple: :globe_with_meridians:

WikiWatershed/model-my-watershed,kdeloach/model-my-watershed,kdeloach/model-my-watershed,kdeloach/model-my-watershed,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,kdeloach/model-my-watershed,kdeloach/model-my-watershed,WikiWatershed/model-my-watershed