Make the Index of a {.incremental} List Block Explicit

[RoyiAvital]

Currently a list described as:

::: {.incremental}
 - Item A.
 - Item B.
 - Item C.
:::

Will generate:

<div>
<ul>
<li class="fragment">Item A.</li>
<li class="fragment">Item B.</li>
<li class="fragment">Item C.</li>
</ul>
</div>

Is there a way to make the code have an explicit data-fragment-index when generating the code (As the order is known)?

So the code will be something like:

<div>
<ul>
<li class="fragment" data-fragment-index="1">Item A.</li>
<li class="fragment" data-fragment-index="2">Item B.</li>
<li class="fragment" data-fragment-index="2">Item C.</li>
</ul>
</div>

The motivation is it will allow easily interacting with other fragmented objects (Appear together or so). See for example #3293.