perf: modify checkbox icon with Liquid

Also optimize list padding start

gulpfile.js/tasks/js.js

@@ -46,7 +46,6 @@ const postJs = () => {
       `${JS_SRC}/commons/*.js`,
       `${JS_SRC}/utils/img-extra.js`,
       `${JS_SRC}/utils/locale-datetime.js`,
-      `${JS_SRC}/utils/checkbox.js`,
       `${JS_SRC}/utils/clipboard.js`,
       // 'smooth-scroll.js' must be called after ToC is ready
       `${JS_SRC}/utils/smooth-scroll.js`
@@ -65,7 +64,6 @@ const categoriesJs = () => {
 const pageJs = () => {
   return concatJs([
       `${JS_SRC}/commons/*.js`,
-      `${JS_SRC}/utils/checkbox.js`,
       `${JS_SRC}/utils/img-extra.js`,
       `${JS_SRC}/utils/clipboard.js`,
       `${JS_SRC}/utils/smooth-scroll.js`