Pos-rich-link allow fetching of resource

[jg10-mastodon-social]

As a dashboard creator, I want to be able to use pos-rich-link in contexts where the resource needs to be loaded in order to display the label and description.

Currently pos-rich-link operates in lazy mode.

This would also assist with #132

[jg10-mastodon-social]

I suggest adding a fetch Boolean attribute that then overrides pos-resource lazy=true

This would allow lazy to remain the default.
The current implementation of pos-list provides an example and precedent for this.

[jg10-mastodon-social]

With #136 this is possible by doing

<pos-resource uri>
  <pos-rich-link/>
</pos-resource>

It would still be more intuitive to have an attribute directly on pos-rich-link