Merge commit '9b0050e9aabe4be65c78ccf292a348f309d50ccd' as 'docs'

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

Closes #11925

docs/content/en/functions/math/Counter.md

@@ -0,0 +1,35 @@
+---
+title: math.Counter
+description: Increments and returns a global counter.
+categories: []
+keywords: []
+action:
+  aliases: []
+  related: []
+  returnType: uint64
+  signatures: [math.Counter]
+---
+
+The counter is global for both monolingual and multilingual sites, and its initial value for each build is 1.
+
+```go-html-template
+{{ warnf "single.html called %d times" math.Counter }}
+```
+
+```sh
+WARN  single.html called 1 times
+WARN  single.html called 2 times
+WARN  single.html called 3 times
+```
+
+Use this function to:
+
+- Create unique warnings as shown above; the [`warnf`] function suppresses duplicate messages
+- Create unique target paths for the `resources.FromString` function where the target path is also the cache key
+
+[`warnf`]: /functions/fmt/warnf
+[`resources.FromString`]: /functions/resources/fromstring
+
+{{% note %}}
+Due to concurrency, the value returned in a given template for a given page will vary from one build to the next. You cannot use this function to assign a static id to each page.
+{{% /note %}}