Fixed code block background color (#596)

Luiz F. A. de Prá

02.15.2021 ee806a669fb86216b4f5823ec32c3164f405b69f

 CONTRIBUTORS.md

@@ -101,4 +101,5 @@
- [kuba86](https://kuba86.com)
- [Vladislav Matus](https://github.com/matusvla)
- [Kirill Feoktistov](https://feoktistoff.org)
- [leins275](https://github.com/LanskovNV)
- [Michael Weiss](https://mweiss.ch)