ExtensionDiff in renderers (just tried console and html)

[Vampire]

I'm implementing ExtensionDiffs, but it seems they don't make it into the renderers, or at least I don't see how they would.
I.e. I'm only using console and html.

The console renderer just lists the route as changed and says there were backward incompatible changes in the spec but no further detail.

The html renderer lists the route under "What's Changed" with an empty <ul> with class detail which then renders as a thick gray line.

It would be nice if the renderers would be able to display details about the extension differences, especially when they are breaking, but also the non-breaking ones would be interesting.

In the html renderer result there is not even an indication whether there were breaking changes or not if the breaking changes come from an extension diff.

[wexom]

This is probably another candidate for labels like enhancement and Render capabilities, similar to #766, #620, and #562.