Readme, and public executable

README.md

@@ -7,3 +7,7 @@ Some references:
 - https://leconjugueur.lefigaro.fr/frlesnombres.php
 - https://www.miakinen.net/vrac/nombres
 - https://www.dcode.fr/ecriture-nombre-lettres
+
+
+Provided as a 1-function library, and a basic command-line utility (`nbr` — will
+certainly be renamed to something longer and less likely to name clash).

bin/dune

@@ -1,3 +1,4 @@
 (executable
  (name nbr)
+ (public_name nbr)
  (libraries nombres))