Add the info on installing kn cli older that latest

Author: rh-max

modules/serverless-installing-cli-linux.adoc

@@ -25,13 +25,16 @@ $ kn: No such file or directory
 .Procedure
 
 . Download the relevant Knative (`kn`) CLI `tar.gz` archive:
-
++
+--
 * link:https://mirror.openshift.com/pub/openshift-v4/clients/serverless/latest/kn-linux-amd64.tar.gz[Linux (x86_64, amd64)]
 
 * link:https://mirror.openshift.com/pub/openshift-v4/clients/serverless/latest/kn-linux-s390x.tar.gz[Linux on IBM Z and LinuxONE (s390x)]
 
 * link:https://mirror.openshift.com/pub/openshift-v4/clients/serverless/latest/kn-linux-ppc64le.tar.gz[Linux on IBM Power (ppc64le)]
-
+--
++
+You can also download any version of `kn` by navigating to that version's corresponding directory in the link:https://mirror.openshift.com/pub/openshift-v4/clients/serverless/[Serverless client download mirror].
 
 . Unpack the archive:
 +

modules/serverless-installing-cli-macos.adoc

@@ -13,6 +13,8 @@ If you are using macOS, you can install the Knative (`kn`) CLI as a binary file.
 .Procedure
 
 . Download the link:https://mirror.openshift.com/pub/openshift-v4/clients/serverless/latest/kn-macos-amd64.tar.gz[Knative (`kn`) CLI `tar.gz` archive].
++
+You can also download any version of `kn` by navigating to that version's corresponding directory in the link:https://mirror.openshift.com/pub/openshift-v4/clients/serverless/[Serverless client download mirror].
 
 . Unpack and extract the archive.
 

modules/serverless-installing-cli-windows.adoc

@@ -13,6 +13,8 @@ If you are using Windows, you can install the Knative (`kn`) CLI as a binary fil
 .Procedure
 
 . Download the link:https://mirror.openshift.com/pub/openshift-v4/clients/serverless/latest/kn-windows-amd64.zip[Knative (`kn`) CLI ZIP archive].
++
+You can also download any version of `kn` by navigating to that version's corresponding directory in the link:https://mirror.openshift.com/pub/openshift-v4/clients/serverless/[Serverless client download mirror].
 
 . Extract the archive with a ZIP program.