build: npm/rake entry point for screenshots upload

We have a Jenkins job to take screenshots of VisualEditor and upload the
result to commons.wikimedia.org. That roughly does:

    npm install
    node_modules/.bin/grunt screenshots-all

    bundle install
    bundle exec upload

However on CI, the Docker container only accepts 'npm run-script XXX' or
'bundle exec rake YYY'.

Add a npm script 'screenshots-all' invoking 'grunt screenshots-all'.

Add a rake task 'commons_upload'. I have added a basic check to make
sure environment variables are properly set before invoking the upload
script.

Thus on CI the usage will become:

  npm install
  npm run-script screenshots-all

  bundle install
  bundle exec rake commons_upload

Which match the CI convention.

Bug: T189122
Change-Id: I221ed8d6178dd036eac287f0f811834a6d4ffd22

Rakefile

@@ -13,3 +13,16 @@ task :default => [:test]
 
 desc 'Run all build/tests commands (CI entry point)'
 task :test => [:rubocop]
+
+desc 'Upload screenshots to commons.wikimedia.org'
+task :commons_upload do
+  require 'commons_upload'
+  required_envs = %w[
+    MEDIAWIKI_API_UPLOAD_URL
+    MEDIAWIKI_USER
+    MEDIAWIKI_PASSWORD
+  ]
+  has_all_envs = required_envs.all? { |env| ENV.key?(env) }
+  fail "Requires env variables:\n#{required_envs}" unless has_all_envs
+  CommonsUpload.images
+end

package.json

@@ -6,7 +6,8 @@
 	"scripts": {
 		"test": "grunt test",
 		"doc": "jsduck",
-		"postdoc": "grunt copy:jsduck"
+		"postdoc": "grunt copy:jsduck",
+		"screenshots-all": "grunt screenshots-all"
 	},
 	"devDependencies": {
 		"babel-polyfill": "6.9.1",