message: plugins/graphiql: add publishing config
diff: {
  "name": "@backstage/plugin-graphiql",
  + "description": "Backstage plugin for browsing GraphQL APIs",
  "version": "0.1.1-alpha.4",
  + "private": false,
  + "publishConfig": {
  + "access": "public"
  + },
  + "homepage": "https://github.com/spotify/backstage/tree/master/plugins/graphiql#readme",
  + "repository": {
  + "type": "git",
  + "url": "https://github.com/spotify/backstage",
  + "directory": "plugins/graphiql"
  + },
  + "keywords": [
  + "backstage"
  + ],
  + "license": "Apache-2.0",
  "main": "dist/index.cjs.js",
  "types": "dist/index.d.ts",
  - "license": "Apache-2.0",
  - "private": true,
  "scripts": {
  "build": "backstage-cli plugin:build",
  "start": "backstage-cli plugin:serve",
  "react": "16.13.1",
  "react-dom": "16.13.1",
  "react-use": "^13.0.0"
  - }
  + },
  + "files": [
  + "dist"
  + ]
  }
  