doc: add reference to Gerrit its-storyboard plugin
doc: add reference to Gerrit its-storyboard plugin

Change-Id: Idefa8e1197a7e5e7fada76655874373074fb740f

WANdisco/gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,gerrit-review/gerrit,GerritCodeReview/gerrit,gerrit-review/gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,gerrit-review/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,gerrit-review/gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,WANdisco/gerrit,gerrit-review/gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,gerrit-review/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,gerrit-review/gerrit