Moved the release notes to the legacy repo
Added download section for to the v3.1.15 releases
Updated the roadmap
Renamed 'Dismissible alert' to 'Collapsible alerts'

This improves the clarity of the purpose
of the plugin.
Merge pull request #6084 from LaurentGoderre/move-release-notes

Moved the release notes to the legacy repo
Update the v3.1 banner on the Web site to reflect that v3.1 is no longer supported and has been moved to wet-boew-legacy.
Merge pull request #6086 from Pacoup/dismiss-alert-name-change

Renamed 'Dismissible alert' to 'Collapsible alerts'
Merge pull request #6085 from thomasgohard/update-v3.1-notice

Update the v3.1 banner on the Web site to reflect that v3.1 is no longer supported and has been moved to wet-boew-legacy.