feat: PATH fix to add raw git path for Unity Package Manager Issue

I don't want to touch git Manifest.

ScoopInstaller/Scoop#4317 (comment)
https://issuetracker.unity3d.com/issues/package-resolution-error-when-using-a-git-dependency-referencing-an-annotated-tag-in-its-git-url?_ga=2.164640191.1854444799.1619404631-1321912765.1607477419

etc/windows/add-gitpath.ps1

@@ -0,0 +1,17 @@
+$gitCmdPath = "${env:USERPROFILE}\scoop\apps\git\current\cmd"
+$userPath = [Environment]::GetEnvironmentVariable("PATH", [EnvironmentVariableTarget]::User)
+# git path exists?
+if (-not (Test-Path "${env:USERPROFILE}\scoop\shims\git.exe")) {
+  Write-Output "git not found in scoop PATH. Please run ``scoop install git`` first."
+} else {
+  # add scoop git raw path to 1st PATH index.
+  if ($userPath.Split(";") -notcontains "$gitCmdPath") {
+    $newUserPath = $gitCmdPath + ";" + $userPath
+    Write-Warning "git cmd not found in your PATH, let's replace to `"$newUserPath`". Old Path is $userPath"
+    [Environment]::SetEnvironmentVariable("PATH", $newUserPath, [EnvironmentVariableTarget]::User)
+    Write-Output "Complete. New PATH is $([Environment]::GetEnvironmentVariable("PATH", [EnvironmentVariableTarget]::User))"
+
+  } else {
+    Write-Output "git cmd is already in your PATH. $userPath"
+  }
+}