isbn-verifier: add EOF newline
This fix the issue that `configlet generate .` is not idempotent as the
track's README might manually adjust for the newline instead.
@@ -40,6 +40,7 @@ Now, it's even trickier since the check digit of an ISBN-10 may be 'X' (represen
* Generate a valid ISBN-13 from the input ISBN-10 (and maybe verify it again with a derived verifier).
* Generate valid ISBN, maybe even from a given starting ISBN.
+
## Rust Installation
Refer to the [exercism help page][help-page] for Rust installation and learning
