Merge commit '9b0050e9aabe4be65c78ccf292a348f309d50ccd' as 'docs'

```
git subtree add --prefix=docs/ https://github.com/gohugoio/hugoDocs.git master --squash
```

Closes #11925

docs/content/en/functions/lang/Merge.md

@@ -0,0 +1,29 @@
+---
+title: lang.Merge
+description: Merge missing translations from other languages.
+categories: []
+keywords: []
+action:
+  aliases: []
+  related: []
+  returnType: any
+  signatures: [lang.Merge FROM TO]
+aliases: [/functions/lang.merge]
+---
+
+As an example:
+
+```sh
+{{ $pages := .Site.RegularPages | lang.Merge $frSite.RegularPages | lang.Merge $enSite.RegularPages }}
+```
+
+Will "fill in the gaps" in the current site with, from left to right, content from the French site, and lastly the English.
+
+A more practical example is to fill in the missing translations from the other languages:
+
+```sh
+{{ $pages := .Site.RegularPages }}
+{{ range .Site.Home.Translations }}
+{{ $pages = $pages | lang.Merge .Site.RegularPages }}
+{{ end }}
+ ```