Implement language service

[madskristensen]

Must haves

• [x] Syntax highlighting (colorizer)
• [x] Tools | Options page (under Text Editors -> Docker File)
• [x] Comment/uncomment support
• [x] Dark theme support

  Nice to haves

• [x] Auto-completion of quotes and braces
• [x] Validation of unknown keywords
• [x] Intellisense for keywords
• [x] Keyword hover tooltips
• [x] Brace completion
• [x] Outlining/code folding
• [x] Signature help
• [ ] Code snippets

[madskristensen]

This is what it currently looks like:

[madskristensen]

Quick info tooltips added:

[madskristensen]

Outlining added:

[madskristensen]

Added dark theme support:

[madskristensen]

Added signature help: