Setting Azure DevOps variable as secret

[stijnmoreels]

Is your feature request related to a problem? Please describe.
Currently, we provide the capability to set an Azure DevOps pipeline variable in our Arcus.Scripting.DevOps PowerShell module, but this functionality does not provide any switch parameter to save the variable as a 'secret' pipeline variable (value won't be shown in logs).

Describe the solution you'd like
Add a switch parameter to the Set-AzDevOpsVariable command so that we can save secret pipeline variables.

Additional context
Marking a pipeline variable as a secret is done by adding issecret=true to the outputed text:

Write-Host "##vso[task.setvariable variable=$secretName;issecret=true]$secretValue`