Package take over: OneTuple

[George Wilson]

Hi all,

Here are my two cents. Disclaimer: I'm another Hackage Trustee and I
care about this for the same reason Oleg does (specifically: the
transitive closure of `diagrams`)

> Would it be worth trying to consolidate similar data structures and
> have Chart + diagrams migrate to Only [1] (which is up to date)?
>
> [1]: https://hackage.haskell.org/package/Only

I have suggested that here
https://github.com/DavidM-D/indexed-list-literals/issues/1
Definitely in the longer term, I'd rather see a move to the Only
package. But in the short term I'd find it much easier to get current
packages working on GHC 8.4 if OneTuple supported 8.4. Oleg's changes
look sensible to me, and adding a co-maintainer seems reasonable given
that the last release was nine years ago and the sole maintainer seems
uncontactable.

My preferred course of action would be to add Oleg as a co-maintainer,
and move downstream packages to `Only` over time. I intend to
participate in the latter.

Cheers,
George