IntelliSense for Marp directives

[yhatt]

Added the basic IntelliSense support for Marp directive. Resolves #158.

Features

• Hit Ctrl + Space in Markdown front-matter or HTML comments to open IntelliSense for Marp directives. Auto completion items are available only when marked Markdown by marp: true.

  If hitted Ctrl + Space again, user can peek the quick help of Marp directives.

  

• A help can peek also when hovered on the recognized directive.

  

• Recognized known directives will be highlighted by Marp's brand color. This visualization may help to find meaningless directives. In addition, we have different text style between global directive and local directive.

  

  The color is defined as marp.directiveKeyForeground and the other VS Code themes can change it (if supported).

Supported directives

Marp for VS Code is depending on all of Marp official toolset. Thus, following directives are all of directives Marp provided.

• Marp for VS Code
  • marp global directive (Only in the front-matter)
• Marpit
  • Global directives
    • theme
    • style
    • headingDivider
  • Local directives
    • paginate
    • header
    • footer
    • class
    • backgroundColor
    • backgroundImage
    • backgroundPosition
    • backgroundRepeat
    • backgroundSize
    • color
• Marp Core
  • size global directive
• Marp CLI
  • title global directive
  • description global directive
  • url global directive
  • image global directive