message: Add clean:* scripts.
diff: "scripts": {
  "watch:css": "postcss src/assets/global.pcss -o static/global.css -w",
  "watch:dev": "sapper dev --ext '.md .svelte'",
  - "clean": "rm -fr ./__sapper__",
  - "dev": "run-p watch:*",
  + "clean": "run-p clean:*",
  + "clean:css": "rm static/global.css",
  + "clean:dev": "rm -fr ./__sapper__",
  + "dev": "npm run clean && run-p watch:*",
  "copyDocsImages": "cp ./",
  "build": "run-s build:css build:sapper",
  "build:css": "NODE_ENV=production postcss src/assets/global.pcss -o static/global.css",
  