hexnumber: add hexnumber entry in plugins README
@@ -160,6 +160,7 @@ Transformations:
- [keytometa](keytometa/) transforms keys to metadata
- [rename](rename/) renames keys according to different rules
- [boolean](boolean/) canonicalizes boolean keys
+- [hexnumber](hexnumber/) converts between hexadecimal and decimal
Doing other stuff:
