Deprecate 'operator-sdk add crd' cmd

Hide `add crd` command and add deprecation message.

cmd/operator-sdk/add/crd.go

@@ -32,6 +32,13 @@ import (
 // newAddCRDCmd - add crd command
 func newAddCRDCmd() *cobra.Command {
 	crdCmd := &cobra.Command{
+		Deprecated: `Use 'operaot-sdk add api' command to create a new API definition for a custom resource.  
+
+'add api' will generate or update CRDs for a particular GVK based on values ` +
+			`provided to '--kind' and '--api-version' specified in the command.
+
+Refer to 'https://sdk.operatorframework.io/docs/cli/operator-sdk_add_api/' for more details.
+		`,
 		Use:   "crd",
 		Short: "Adds a Custom Resource Definition (CRD) and the Custom Resource (CR) files",
 		Long: `The operator-sdk add crd command will create a Custom Resource Definition (CRD)` +

website/content/en/docs/cli/operator-sdk_add.md

@@ -20,5 +20,4 @@ Adds a controller or resource to the project
 * [operator-sdk](../operator-sdk)	 - An SDK for building operators with ease
 * [operator-sdk add api](../operator-sdk_add_api)	 - Adds a new api definition under pkg/apis
 * [operator-sdk add controller](../operator-sdk_add_controller)	 - Adds a new controller pkg
-* [operator-sdk add crd](../operator-sdk_add_crd)	 - Adds a Custom Resource Definition (CRD) and the Custom Resource (CR) files