use terser and clean-css directly

create a sourcemap as well by default

node_modules/.bin/esvalidate.ps1

@@ -0,0 +1,18 @@
+#!/usr/bin/env pwsh
+$basedir=Split-Path $MyInvocation.MyCommand.Definition -Parent
+
+$exe=""
+if ($PSVersionTable.PSVersion -lt "6.0" -or $IsWindows) {
+  # Fix case when both the Windows and Linux builds of Node
+  # are installed in the same directory
+  $exe=".exe"
+}
+$ret=0
+if (Test-Path "$basedir/node$exe") {
+  & "$basedir/node$exe"  "$basedir/../esprima/bin/esvalidate.js" $args
+  $ret=$LASTEXITCODE
+} else {
+  & "node$exe"  "$basedir/../esprima/bin/esvalidate.js" $args
+  $ret=$LASTEXITCODE
+}
+exit $ret