tpl/lang: Add new localized versions of lang.FormatNumber etc.

Fixes #8820

docs/content/en/functions/lang.md

@@ -0,0 +1,30 @@
+---
+title: lang
+package: lang
+description: "TODO.."
+date: 2021-07-28
+categories: [functions]
+keywords: [numbers]
+menu:
+  docs:
+    parent: "functions"
+toc: false
+signature: ["lang.NumFmt PRECISION NUMBER [OPTIONS [DELIMITER]]"]
+aliases: ['/functions/numfmt/']
+type: 'template-func'
+---
+
+The default options value is `- . ,`.  The default delimiter within the options
+value is a space.  If you need to use a space as one of the options, set a
+custom delimiter.s
+
+Numbers greater than or equal to 5 are rounded up. For example, if precision is set to `0`, `1.5` becomes `2`, and `1.4` becomes `1`.
+
+```
+{{ lang.NumFmt 2 12345.6789 }} → 12,345.68
+{{ lang.NumFmt 2 12345.6789 "- , ." }} → 12.345,68
+{{ lang.NumFmt 0 -12345.6789 "- . ," }} → -12,346
+{{ lang.NumFmt 6 -12345.6789 "- ." }} → -12345.678900
+{{ lang.NumFmt 6 -12345.6789 "-|.| " "|" }} → -1 2345.678900
+{{ -98765.4321 | lang.NumFmt 2 }} → -98,765.43
+```