Syntax highlighting

Cornifer comes with a comprehensive C4 DSL grammar, which allows powerful syntax highlighting. Color schema is aligned with semantic convention we agreed upon.

At the time of writing, language server has not been implemented yet, preventing extension to provide error checks. In the meanwhile, a tacit workaround is to assume that if you read/write a line w/o any colors, this line is wrong ie conflicts with the underlying grammar (either misspelled or wrongly placed). Hover facility is at the rescue to provide guidance.