In the docs we have this feature of Frontity.
Is this extensibility refered to “packages”?
What was the purpose of this page linked in this section → https://github.com/frontity/docs/blob/a6a79476ae299fdebf52cf13ddeaca9ede179f24/docs/frontity-features/extensions.md ?
What is this “interface tools” refering to?
Yes, I think most extensibility in Frontity is based on packages, although not exclusively because there are more ways to extend or “reuse code” in Frontity, like exposing components, hooks, handlers, processors… that you can import in a site/theme/package.
The text you show in the image was written when we launched the 1.0 version.
We had a rough idea of the types of packages we could release, based on the previous version of the framework. I guess that list still applies. Maybe you can reduce it to the packages available today and either remove the ones we haven’t released yet or at least mention that we may work on the in the future (although no ETA is available).
I think we meant the things that are not packages, like components, hooks, handlers, processors… I think you can find a better name or not name at all 
From the list described in that image, I think context routing doesn’t apply because for the moment we don’t have a plan to create a more complex router than tiny-router. Swipe navigation is something we have started researching but we are not sure yet if we could make a hook that is as simple to use as the infinite scroll yet. Gutenberg2React was an idea that maybe in the future we would need a substitute for Html2React that was more focused on Gutenberg blocks instead of just HTML, but we have not seen the need for that yet and our current idea is to improve HTML2React instead, so maybe you can remove it. Apart from that, I think we have AutoPrefetching thanks to the <Link> component, which is not a package, but it is also part of Frontity’s extensibility. So I guess you could add it to that category as well.
