Releases: Add cross-referencing among listing pages

Make the two home pages that list Gerrit releases link to each other. Do
so in order to help maintaining support statuses consistency between the
two pages. Doing so should also help readers find related information.

Fix a double blank line markdown lint issue in changed releases README.

Change-Id: Ie06775c7eb7b7eef40ff6d2a0d03605030a8d98d
2 files changed