Arbitrary HTML asset aggregation

We already have CSS/JS asset aggregation. I’d like to see this with arbitrary HTML too. Think of a single WebC component file for a web font that includes both the @font-face CSS and the preload HTML together! Or a WebC icon that only includes a single <g> that aggregates up to a reusable de-duplicated SVG icon set.

<style webc:bucket="priority">
@font-face {
  src: url("font.woff2") format("woff2");
}
</style>

<template webc:bucket="header">
  <link rel="preload" href="font.woff2" as="font" type="font/woff2" crossorigin>
</template>

<template webc:bucket="svg-icon">
  <g id="icon-arrow”>
    <path d="…"></path>
  </g>
</template>

Start by locating the existing CSS/JS asset aggregation implementation and its entry points. Define how bucketed template HTML should be collected, emitted, and de-duplicated for font preload and SVG icon examples, then verify the behavior alongside the existing aggregation functionality.