Add information about contributing to the CLI documentation. (#2649)

* Add information about contributing to the CLI documentation.

* Fix typo

Author: etabakov

CONTRIBUTING.md

@@ -105,5 +105,18 @@ When the patch is reviewed and merged, you can safely delete your branch and pul
 
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+Updating the CLI documentation
+===
+
+The CLI documentation is what you see when running the `tns help` command. 
+This documentation is distributed as part of the CLI package and is generated from the *.md files that can be found in <a href="https://github.com/NativeScript/nativescript-cli/tree/master/docs/man_pages" target="_blank">man_pages folder</a>
+The output of the documentation is html static pages that are generated on post install hook of the CLI installation. 
+In addition, documentation generation is triggered every time there is no html article for the respective help command that is executed.
+
+In order to see a change applied in your development workspace after editing the *.md files, you can use the `tns dev-generate-help` command. 
+This will trigger regeneration of all html files on your local environment. Mind that you need to run from the /bin folder of the nativescript_cli.
+
+[Back to Top][1]
+
 [1]: #contribute-to-the-telerik-nativescript-command-line-interface
 [2]: https://github.com/NativeScript/nativescript-cli