Prettify number of issues (#17760)

* Prettify number of issues

- Use the PrettyNumber function to add commas in large amount of issues.

* Use client-side formatting

* prettify on both server and client

* remove unused i18n entries

* handle more cases, support other int types in PrettyNumber

* specify locale to avoid issues with node default locale

* remove superfluos argument

* introduce template helper, octicon tweaks, js refactor

* Update modules/templates/helper.go

* Apply some suggestions.

* Add comment

* Update templates/user/dashboard/issues.tmpl

Co-authored-by: silverwind <me@silverwind.io>

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

web_src/js/utils.js

@@ -90,3 +90,10 @@ export function strSubMatch(full, sub) {
   }
   return res;
 }
+
+// pretty-print a number using locale-specific separators, e.g. 1200 -> 1,200
+export function prettyNumber(num, locale = 'en-US') {
+  if (typeof num !== 'number') return '';
+  const {format} = new Intl.NumberFormat(locale);
+  return format(num);
+}