[🚀es-lazy-template]: lazy-markup component (POC)

[dshovchko]

As ESL consumer, I want to have the ability to load lazily parts of a page.

Potential consumers: ADS / lazy loading for page parts
Original idea: Custom mixin to observe its placement relative to viewport and load markup by the provided URL

• Mixin but not an element
• Use cases:

  <!-- Replace once appear in a viewport -->
  <div esl-lazy-template="../markup.html" >
    <!-- To be loaded when appear in viewport-->
  </div>

  <!-- Replace once appear in a viewport -->
  <template esl-lazy-template="../markup.html" >
    <!-- To be loaded when appear in viewport-->
  </template>

  <!-- Replace once appear in a viewport -->
  <template esl-lazy-template>
      <some content></..>
  </template>