Draft: feat: add COBOL syntax highlighting support
Relates to issue #430705
This MR was created by Duo in Session 1100010
Changes
- Add COBOL language support to highlight.js language loader
- Support for .cob, .cbl, .cpy, and .cpb file extensions
- Integrate highlightjs-cobol third-party plugin for syntax highlighting
- Enable syntax highlighting for COBOL code blocks in GitLab UI