feat(users/Profpatsch/netencode): Add initial Haskell parser

A simple categorical parser that does not implement Monad, and does
not contain an `m` and some rudementary error message handling.

In the future I’d probably want to wrap everything in an additional
`m`, so that subparsers can somehow use `Selective` to throw errors
from within `m` that contain the parsing context if at all possible.
Hard to do without Monad, I have to say. Not even stuff like `StateT`
works without the inner `m` implementing `Monad`.

Change-Id: I1366eda606ddfb019637b09c82d8b0e30bd4e318
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7797
Tested-by: BuildkiteCI
Reviewed-by: Profpatsch <mail@profpatsch.de>

users/Profpatsch/shell.nix

@@ -37,6 +37,7 @@ pkgs.mkShell {
       h.hspec-expectations-pretty-diff
       depot.users.Profpatsch.my-prelude
       depot.users.Profpatsch.netencode.netencode-hs
+      depot.users.Profpatsch.arglib.netencode.haskell
       depot.users.Profpatsch.execline.exec-helpers-hs
 
     ]))