Add Cmajor language support to Github for syntax highlighting, repo search filters, etc.

[runawaykiwi]

If you view Cmajor code on Github, it's plain text. It would be nice to view code with proper syntax highlighting while I am using a web browser. This will also update the language percentage bar on the repo homepage and in turn make it easier to filter for Cmajor files. It will also make it easier to search for Cmajor repositories across GitHub with the language: parameter in the search.

• https://github.com/github-linguist/linguist/tree/main/vendor#grammar-index
• https://github.com/github-linguist/linguist