Add support of nsdiagram dialect

Diagram YAML in a fenced block - might be easier to author in some cases than, say, PlantUML. As it will result in a circular dependency use a service or some other type of registration. A more radical way is to drop the enum altogether and switch to services.

Origin	common/engineering/engineering.yml 16:5
Uri	engineering://nasdanika/modules/core/modules/common/issues/nsdiagram-dialect
Target	Common
Workable