Add requirements to npm module
diff --git a/lib/ansible/modules/packaging/language/npm.py b/lib/ansible/modules/packaging/language/npm.py
index fed13921d00fd8..256218702433ab 100644
--- a/lib/ansible/modules/packaging/language/npm.py
+++ b/lib/ansible/modules/packaging/language/npm.py
@@ -70,6 +70,8 @@
     required: false
     default: present
     choices: [ "present", "absent", "latest" ]
+requirements:
+    - npm installed in bin path (recommended /usr/local/bin)
 '''
 
 EXAMPLES = '''

npm is required in order for this module to work.

##### SUMMARY
<!--- Describe the change, including rationale and design decisions -->

<!---
If you are fixing an existing issue, please include "Fixes #nnn" in your
commit message and your description; but you should still explain what
the change does.
-->

##### ISSUE TYPE
<!--- Pick one below and delete the rest: -->
 - Docs Pull Request

##### COMPONENT NAME
npm