feat: Posh-GitHub / VsVars $PROFILE encoding

- function taken from posh-github, allow us to reliably
   select the appropriate encoding for writing to $PROFILE

Posh-GitHub/Posh-GitHub.nuspec

@@ -48,5 +48,6 @@ that have been merged into the master branch.
   <files>
     <file src="tools\**" target="tools" />
     <file src="..\core\PowerShellHelpers.ps1" target="tools" />
+    <file src="..\core\EncodingHelpers.ps1" target="tools" />
   </files>
 </package>

Posh-GitHub/tools/chocolateyInstall.ps1

@@ -10,6 +10,7 @@ function Get-CurrentDirectory
 try {
   $current = Get-CurrentDirectory
   . (Join-Path $current 'PowerShellHelpers.ps1')
+  . (Join-Path $current 'EncodingHelpers.ps1')
 
   # find user specific module directory
   $moduleDirectory = Get-ModuleDirectory
@@ -57,7 +58,7 @@ try {
   {
     $loaderFile = 'Posh-GitHub-Profile.ps1'
     "`n`n# Load Posh-GitHub`n. '$installDirectory\$loaderFile'" |
-      Out-File -FilePath $PROFILE -Append -Encoding UTF8
+      Out-File -FilePath $PROFILE -Append -Encoding (Get-FileEncoding $PROFILE)
     . $PROFILE
   }