enable source map generation

extensions/emmet/extension.webpack.config.js

@@ -8,8 +8,8 @@
 const path = require('path');
 
 module.exports = {
-	stats: 'errors-only',
-	// mode: 'none', // default is production
+	mode: 'production',
+	// mode: 'none',
 	context: __dirname,
 	target: 'node',
 	resolve: {
@@ -26,4 +26,13 @@ module.exports = {
 	externals: {
 		'vscode': 'commonjs vscode',
 	},
+	stats: 'errors-only',
+	devtool: 'source-map',
+	module: {
+		rules: [{
+			test: /\.js$/,
+			use: ["source-map-loader"],
+			enforce: "pre"
+		}]
+	}
 };