Add recommendation to use Cobra (#368)

* Add recommendation to use Cobra

* dummy commit

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Co-authored-by: steveclay <[email protected]>

Author: lmosca

docs/plugin_developer_guide.md

@@ -80,7 +80,8 @@ IBM Cloud CLI SDK provides a set of APIs to register and manage plug-ins. It als
     - _Version_: The version of plug-in.
     - _MinCliVersion_: The minimal version of IBM Cloud CLI required by the plug-in.
     - _PrivateEndpointSupported_: Indicates if the plug-in is designed to also be used over the private network.
-    - _IsCobraPlugin_: Indicates if the plug-in is built using the Cobra framework
+    - _IsCobraPlugin_: Indicates if the plug-in is built using the Cobra framework.
+      - It is **strongly** recommended that you use this framework to build your plug-in.
     - _Commands_: The array of `plugin.Commands` to register the plug-in commands.
     - _Alias_: Alias of the Alias usually is a short name of the command.
     - _Command.Flags_: The command flags (options) which will be displayed as a part of help output of the command.