Invoke-WebRequest auth headers

Add auth headers when downloading files.  Useful if pulling files directly from an Azure Devops git repo.

 $user = "UsernameLoadedFromSecureStore"  
 $pass = "PasswordLoadedFromSecureStore"  
   
 $pair = "$($user):$($pass)"  
 $encodedCreds = [System.Convert]::ToBase64String([System.Text.Encoding]::ASCII.GetBytes($pair))  
 $basicAuthValue = "Basic $encodedCreds"  
 $Headers = @{Authorization = $basicAuthValue}  
   
 Invoke-WebRequest -Uri $uri -OutFile $filename -Headers $Headers