message: Fix type reference
diff: "module": "build/index.js",
  "unpkg": "build/vega-embed.min.js",
  "jsdelivr": "build/vega-embed.min.js",
  - "types": "build/embed.d.ts",
  + "types": "build/index.d.ts",
  "devDependencies": {
  "@types/d3-selection": "^1.3.0",
  "@types/semver": "^5.5.0",
  