Bump to ES6

backend/gulpfile.babel.js

@@ -0,0 +1,48 @@
+import fs from 'fs';
+import browserify from 'browserify';
+import gulp from 'gulp';
+import prettier from 'gulp-prettier';
+import header from 'gulp-header';
+
+const DEST_FILE = 'sub-store.min.js';
+
+export function styles() {
+	return gulp
+		.src('src/**/*.js')
+		.pipe(
+			prettier({
+				singleQuote: true,
+				trailingComma: 'all',
+				tabWidth: 4,
+				bracketSpacing: true
+			})
+		)
+		.pipe(gulp.dest((file) => file.base));
+}
+
+export function scripts() {
+	return browserify('src/main.js')
+		.transform('babelify', {
+			presets: [
+        [
+          '@babel/preset-env'
+        ]
+			]
+		})
+		.plugin('tinyify')
+		.bundle()
+		.pipe(fs.createWriteStream(DEST_FILE));
+}
+
+export function banner() {
+	const pkg = require('./package.json');
+
+	return gulp
+		.src(DEST_FILE)
+		.pipe(header(fs.readFileSync('./banner', 'utf-8'), { pkg, updated: new Date().toLocaleString() }))
+		.pipe(gulp.dest((file) => file.base));
+}
+
+const build = gulp.series(styles, scripts, banner);
+
+export default build;