Implement custom syntax highlighting in DAG editor

[yottahmd]

Overview
Add syntax highlighting to the DAG editor.

Schema Reference

The schema for the DAG editor can be found here:

• DAG Schema

Resources

Monarch allows the creation of custom language definitions that extend keywords. More details can be found here:

• Monarch Documentation (Upstream)
• Monaco-react Discussion

Guides on how to add custom syntax highlighting in the Monaco editor:

• How to add a custom language to monaco-react

How to implement autocomplete in the Monaco editor:

• Stack Overflow: Implementing autocomplete in Monaco editor

Additional Context

• Dagu YAML intellisense / JSON schema #325
• Our discussion on Discord Channel