There is still some debate about the best way to provide syntax highlighting in Gutenberg. Another implementation called Code Syntax Block by Marcus Kazmierczak, extends Gutenberg’s existing code block to offer syntax highlighting, instead of creating a new block for it. It also uses PrismJS syntax highlighter.

Yet another way to provide syntax highlighting is to do it server-side via PHP instead of using PrismJS to do it client-side with JS. Doing it server-side has the benefit of improving frontend performance. It also works with JS disabled. For more details, see this PR: https://github.com/mkaz/code-syntax-block/pull/13