vanilah web component templates

We have several scenarios where we have custom elements using vanilla web components that do not have a template. The current work around is to just use a empty template so that during the loading process we don't get a error indicating that there must be a template.

Template loading for vanilla web components sound not enforce the presence of a template.
We use this for d3 visualisations where we build up the UI manually.

This issue affects us greatly and we would appreciate any assistance to avoid having to use a empty template tag as that affects content elements.

Start by tracing the template-loading validation for vanilla web components and reproduce the issue with a custom element that has no template, including the d3 visualization scenario described. Done means such elements load without an empty template while existing elements that use templates continue to work.

Written by the indexing model from the issue text.