feat: OP Environment ( Fixes #1 )

Setting env:OpenPackagePath in psm1.  Writing a better warning for PowerShell 5.1

Author: StartAutomating

OP.psm1

@@ -7,11 +7,23 @@ foreach ($file in Get-ChildItem -Path $CommandsPath -Filter '*-*.ps1') {
 }
 
 if (-not ('IO.Packaging.Package' -as [type])) {
-    $addedTypes = Add-type -AssemblyName System.IO.Packaging -PassThru
-    $packageTypeFound = $addedTypes | Where-Object FullName -eq 'System.IO.Packaging.Package'
-    if (-not $packageTypeFound) {
-        Write-Warning "Could not find [IO.Packaging.Package]"
-    }
+    if ($psVersionTable.PSVersion -ge '6.0') {
+        $addedTypes = Add-type -AssemblyName System.IO.Packaging -PassThru
+        $packageTypeFound = $addedTypes | Where-Object FullName -eq 'System.IO.Packaging.Package'
+        if (-not $packageTypeFound) {
+            Write-Warning "Could not find [System.IO.Packaging.Package]"
+        }
+    } else {        
+        Write-Warning (
+            @(
+                "System.IO.Packaging.Package is not included with Windows PowerShell."
+                "Please download System.IO.Packaging from Nuget:"
+                "https://www.nuget.org/packages/System.IO.Packaging/"
+            ) -join [Environment]::NewLine
+        )  
+    }    
 }
 
-
+if (-not $env:OpenPackagePath) {
+    $env:OpenPackagePath = Join-Path $home OpenPackage 
+}