upd README with 2023 instructions

Author: ulysses4ever

Diff for: README.md

@@ -5,6 +5,15 @@ Below are instructions on how to run the solutions.
 
 [aoc]: https://adventofcode.com/
 
+## 2023 (and somewhat 2019)
+
+Make sure to clone `--recursive`ly because we now depend on a library
+(`aoc-lib`) that lives here as a submodule.
+
+```shell
+cat Y2023/input/day-1.txt | cabal run y2023:day-1
+```
+
 
 ## 2022