Add Topiary v0.2.3

[Niols]

Website: https://topiary.tweag.io/
Repository: https://github.com/tweag/topiary
Release: https://github.com/tweag/topiary/releases/tag/v0.2.3
Change log: https://github.com/tweag/topiary/blob/v0.2.3/CHANGELOG.md

Additionally:

• Update homepage of past versions to match https://topiary.tweag.io/
• Add description to all version to match the one on the website above.
• Mark Topiary v0.2.2 as broken (because of Catastrophic performances on OCaml files tweag/topiary#519). The technique used was found in mark packages as broken opam#2824.

[mseri]

Looks fine, thanks.
I am going to accept this. We usually use available: false but I like the extra readabilty of the error in this case:

[ERROR] topiary = 0.2.2: unmet availability conditions: 'broken'