Emails: resurrect template notification (#18686)

* Emails: resurrect template notification

* Phantomjs (oh yeah, there is another dev dep phantom :-) was failing for
  the generation of the html templates so I had to update the dependencies
  in order to fix it. While doing that I update the scripts field and docs
  for it as well. yarn.lock is included

* Move splitting of the emails to separate helper function, since more services
  coming up that would need to use this functionality

* Add support for enterprise specific email letters. Probably could
  be done in the better way, but it's not a priority right now

emails/README.md

@@ -1,9 +1,15 @@
+## Prerequisites
 
 - npm install
 - gem install premailer
-- grunt   (default task will build new inlines email templates)
-- grunt watch  (will build on source html or css change)
 
-assembled email templates will be in dist/ and final
-inlined templates will be in ../public/emails/
+## Tasks
+
+- npm run build (default task will build new inlines email templates)
+- npm start (will build on source html or css change)
+
+## Result
+
+Assembled email templates will be in `dist/` and final
+inlined templates will be in `../public/emails/`