The product field of the release note and change forms has no placeholder

Problem

The "Add Release Note" form of the application home page and the "Add Release Change" form of Code/HomeReleaseChanges each pair a product input with a version input. The version input tells the user what to type through a placeholder attribute. The product input has no prompt at all: its only content is the default product name read from Code/ReleaseNotesConfig.

Since RN-77 ships an empty default product name, so that the administrator has to choose one, the product input renders as an empty box with nothing in it, next to a version box that reads "e.g. 8.3-milestone-1". Reported on xwiki.org by Simon Urli, see the attached screenshot.

RN-93 then gave every text input of the three forms both a <label> and a placeholder – except the two product inputs, which got only a label. They are still the only text inputs of these forms with no prompt of their own.

Fix

Give the two product inputs a placeholder, through new releasenotes.releases.add.product.placeholder and releasenotes.changes.add.product.placeholder translation keys, like every other text input of these forms.