new: pwsh : luajit installation script

bin/windows/luajit/install_luajit.ps1

@@ -0,0 +1,22 @@
+# installing luajit under %localappdata%\Programs
+
+# download and build
+git clone https://luajit.org/git/luajit.git
+cd luajit
+make
+
+# installing
+$luajit_location = Join-Path $env:LOCALAPPDATA "Programs\luajit"
+mkdir $luajit_location
+cp .\src\luajit.exe, .\src\lua51.dll $luajit_location
+mkdir $luajit_location\lua
+mkdir $luajit_location\lua\jit
+cp .\src\jit\* $luajit_location\lua\jit
+
+# add to path
+while($true) {
+  $input = Read-Host "add $env:LOCALAPPDATA\Programs\luajit to `$PATH. (Y)"
+  if ($input = 'Y') {
+	break
+  }
+}