Rudder

With some front-end dependencies (see #27103) we now have ESM modules coming in step by step to change the way we use javascript in the browser, and we need support to use such modules.

In practice, we need ways to define <script type="module"> import ... from '/rudder/cache-x.x/javascript/lib' </script>, which are not baked into Liftweb so we need several utils and ways to import known JS resources