[data/C/books-and-ebooks/0002-fedora-defensive-coding.json] date field isn't applied from the JSON file to the README.md

After running src/compiler.php the date is ignored:

$ grep -r date data/C/books-and-ebooks/0002-fedora-defensive-coding.json 
    "date": "2012",

• README.md:

-      * [Defensive Coding: A Guide to Improving Software Security by the Fedora Security Team](#defensive-coding-a-guide-to-improving-software-security-by-the-fedora-security-team-2018) (2018)
+      * [Defensive Coding: A Guide to Improving Software Security by the Fedora Security Team](#defensive-coding-a-guide-to-improving-software-security-by-the-fedora-security-team-2019) (2019)

• src/Util.php:

        if (!empty($fd['date'])) {
            $dt = new \DateTime($fd['date']);
            $header .= ' ('.$dt->format('Y').')';
        }

• DateTime:

Instead of just using the year, it seems working when date matches the pattern "YYYY-MM"

https://github.com/paragonie/awesome-appsec/blob/master/data/C/books-and-ebooks/0002-fedora-defensive-coding.json#L2

• Notes:

OK: Four digit year and month (GNU) YY "-" mm "2008-6", "2008-06", "1978-12"
NOK: Year (and just the year) YY "1978", "2008"
https://www.php.net/manual/pt_BR/datetime.construct.php#123882
https://www.php.net/manual/pt_BR/datetime.construct.php#119591
https://www.php.net/manual/en/datetime.formats.date.php)

• Enhancement:

Include optional fields and examples.