Added yarn ship for publishing to npm/unpkg

refs https://github.com/TryGhost/members.js/issues/5

We use `yarn ship` across all our packages for publishing new versions.

ghost/portal/README.md

@@ -85,9 +85,8 @@ See the section about [running tests](https://facebook.github.io/create-react-ap
 
 ## Publish
 
-Before shipping, please ensure the intended version is updated in `package.json`.
-
-- Run `npm publish --access public` to ship the new version to npm and unpkg.
+- `yarn ship` is an alias for `npm publish`
+    - Before shipping, please ensure the intended version is updated in `package.json`.
     - Builds the script with latest code using `yarn build` (prePublish)
     - Publishes package on npm as `@tryghost/members-js` and creates an unpkg link for script at https://unpkg.com/@tryghost/members-js@VERSION
 

ghost/portal/package.json

@@ -10,6 +10,9 @@
     "LICENSE",
     "README.md"
   ],
+  "publishConfig": {
+    "access": "public"
+  },
   "dependencies": {
     "@testing-library/jest-dom": "4.2.4",
     "@testing-library/react": "9.5.0",
@@ -27,6 +30,7 @@
     "test": "react-scripts test",
     "eject": "react-scripts eject",
     "lint": "eslint src --ext .js --cache",
+    "ship": "npm publish",
     "posttest": "yarn lint",
     "prepublishOnly": "yarn build"
   },