Use Babel and ES6 in docs JS files (#31607)

* Pass docs js through Babel

* Use ES6 in docs js

* Only run babel on src files

* Allow babel in Hugo

* Update scripts.html

* Inherit from the root .eslintrc.json

* Use `Array.from`

* Drop Babel from docs

* Prefer template

* replace IIFE with arrow functions

Co-authored-by: XhmikosR <xhmikosr@gmail.com>
Co-authored-by: GeoSot <geo.sotis@gmail.com>

site/content/docs/5.1/examples/sidebars/sidebars.js

@@ -1,8 +1,8 @@
 /* global bootstrap: false */
-(function () {
+(() => {
   'use strict'
-  var tooltipTriggerList = Array.prototype.slice.call(document.querySelectorAll('[data-bs-toggle="tooltip"]'))
-  tooltipTriggerList.forEach(function (tooltipTriggerEl) {
+  const tooltipTriggerList = Array.from(document.querySelectorAll('[data-bs-toggle="tooltip"]'))
+  tooltipTriggerList.forEach(tooltipTriggerEl => {
     new bootstrap.Tooltip(tooltipTriggerEl)
   })
 })()