install: create install script for windows

install.ps1

@@ -0,0 +1,19 @@
+Param(
+   [Parameter(Mandatory=$true)]
+   [ValidateSet('npm','yarn','pnpm', ErrorMessage = 'Must provide node.js package manager')]
+   [string]$package_manager
+)
+
+git clone 'https://github.com/wix/import-cost.git'
+if (-not $?) {
+   Write-Host 'Failed to clone wix/import-cost' -ForegroundColor Red
+   exit 1
+}
+
+cd import-cost
+if (-not $?) { exit 1 }
+iex "$package_manager install"
+cd ..
+
+cp .\index.js .\import-cost\index.js
+