Add pwsh PowerShell interpreter (#4073)

* Register pwsh as interpreter for PowerShell

* Add pwsh sample

* Remove pwsh from Shell section

lib/linguist/languages.yml

@@ -3526,6 +3526,8 @@ PowerShell:
   - ".ps1"
   - ".psd1"
   - ".psm1"
+  interpreters:
+  - pwsh
   language_id: 293
 Processing:
   type: programming

samples/PowerShell/pwsh-shebang.ps1

@@ -0,0 +1,21 @@
+#!/usr/bin/env pwsh
+
+# source:  https://github.com/PowerShell/PowerShellStandard/blob/3436bfc162d6804dd11d1d76c4faff486b4b405d/build.ps1
+
+param ( 
+    [Parameter(ParameterSetName="Clean")][switch]$Clean,
+    [Parameter(ParameterSetName="Test")][switch]$Test
+)
+
+import-module $PSScriptRoot/PowerShellStandard.psm1 -force
+
+if ( $Clean ) {
+    Start-Clean
+    return
+}
+
+Start-Build
+
+if ( $Test ) {
+    Invoke-Test
+}