Code Syntax Block extends the WordPress block editor by adding syntax highlighting support to the core code block using the Prism syntax highlighter.
The Prism syntax highlighter runs JavaScript loaded on the front-end to parse code blocks and apply syntax markup. A CSS file specifies the color and style to apply to that markup. See Prism syntax highlighter for full details.
Primary development and issues tracked on Github at: https://github.com/mkaz/code-syntax-block
