Add a "Free" renderer implementation of IsBlock/IsInline

I've recently embedded this library in my tool to generate my [blog](https://lucasdicioccio.github.io/how-this-blog-works.html) and I find it pretty cool as a user. So first-of all thanks.

Some context, the sort of things I want to do are vanity analytics about my content (much like the article<>topic graph on the homepage).

For such analytics, I realize I will have to run a number of statistics on the _structure_ of the parsed blocks/inlines. Choices I have found so far are either:
- one renderer per 'statistics' (e.g., collect the links so that I can draw a graph between articles, tell which website I link the most etc.)
- one generic data-structure collector that I can then consume and pattern-match on

For the 2nd case, I think I'm about to implement the 'most mundane' implementation: a free implementation of IsBlock/IsInline/HasAttributes with a datatype that has one constructor per typeclass function, and wrapped in a newtyped list to get the Nonoid for free as well.

Do you foresee any issue with this approach? at first glance I think it's definitely approachable. Would you mind a PR adding it to this directory if needed (I've heard ZuriHac 2022 is approaching and it seems like a good project to hack on)?