Merge commit '9b0050e9aabe4be65c78ccf292a348f309d50ccd' as 'docs'

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

Closes #11925

docs/content/en/functions/crypto/HMAC.md

@@ -0,0 +1,31 @@
+---
+title: crypto.HMAC
+description: Returns a cryptographic hash that uses a key to sign a message.
+categories: []
+keywords: []
+action:
+  aliases: [hmac]
+  related:
+    - functions/crypto/FNV32a
+    - functions/crypto/MD5
+    - functions/crypto/SHA1
+    - functions/crypto/SHA256
+  returnType: string
+  signatures: ['crypto.HMAC HASH_TYPE KEY MESSAGE [ENCODING]']
+aliases: [/functions/hmac]
+---
+
+Set the `HASH_TYPE` argument to `md5`, `sha1`, `sha256`, or `sha512`.
+
+Set the optional `ENCODING` argument to either `hex` (default) or `binary`.
+
+```go-html-template
+{{ hmac "sha256" "Secret key" "Secret message" }}
+5cceb491f45f8b154e20f3b0a30ed3a6ff3027d373f85c78ffe8983180b03c84
+
+{{ hmac "sha256" "Secret key" "Secret message" "hex" }}
+5cceb491f45f8b154e20f3b0a30ed3a6ff3027d373f85c78ffe8983180b03c84
+
+{{ hmac "sha256" "Secret key" "Secret message" "binary" | base64Encode }}
+XM60kfRfixVOIPOwow7Tpv8wJ9Nz+Fx4/+iYMYCwPIQ=
+```