fix(gulpfile): 完善打包配置

1. production 时自动压缩
2. 新增 banner  target 配置

gulpfile.js

@@ -222,7 +222,9 @@ async function core() {
         globalName: 'luckysheet',    
         entryPoints: ['src/index.js'],
         bundle: true,
-        // minify: true,
+        minify: production,
+        banner: { js: banner },
+        target: ['es2015'],
         sourcemap: true,
         outfile: 'dist/luckysheet.umd.js',
         logLevel: 'error',