As mentioned on
https://stackoverflow.com/questions/729692/why-should-text-files-end-with-a-newline
and
https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_206,
POSIX defines a line as

> A sequence of zero or more non- <newline> characters plus a terminating <newline>
> character.

When a file does not terminate with an empty line, `Git` commands such
as `git diff` show the message `No newline at end of file`.

This commit adds a CI job `pre-commit` to enforce the formatting.