refactor(build): modularize JS code

- replace gulp with rollup
- remove JS output from repo

package.json

@@ -11,19 +11,25 @@
   "bugs": {
     "url": "https://github.com/cotes2020/jekyll-theme-chirpy/issues"
   },
-  "homepage": "https://github.com/cotes2020/jekyll-theme-chirpy#readme",
+  "homepage": "https://github.com/cotes2020/jekyll-theme-chirpy/",
   "scripts": {
+    "prebuild": "npx rimraf assets/js/dist",
+    "build": "NODE_ENV=production npx rollup -c --bundleConfigAsCjs",
+    "prewatch": "npx rimraf assets/js/dist",
+    "watch": "npx rollup -c --bundleConfigAsCjs -w",
     "test": "npx stylelint _sass/**/*.scss",
-    "fixlint": "npx stylelint _sass/**/*.scss --fix"
+    "fixlint": "npm run test -- --fix"
   },
   "devDependencies": {
-    "gulp": "^4.0.2",
-    "gulp-concat": "^2.6.1",
-    "gulp-insert": "^0.5.0",
-    "gulp-rename": "^2.0.0",
-    "gulp-uglify": "^3.0.2",
+    "@babel/core": "^7.21.0",
+    "@babel/plugin-proposal-class-properties": "^7.18.6",
+    "@babel/preset-env": "^7.20.2",
+    "@rollup/plugin-babel": "^6.0.3",
+    "@rollup/plugin-terser": "^0.4.0",
+    "rimraf": "^4.4.0",
+    "rollup": "^3.19.1",
+    "rollup-plugin-license": "^3.0.1",
     "stylelint": "^15.2.0",
-    "stylelint-config-standard-scss": "^7.0.1",
-    "uglify-js": "^3.17.4"
+    "stylelint-config-standard-scss": "^7.0.1"
   }
 }