Automate the Hugo release process

This commit adds a work flow aroung GoReleaser to get the Hugo release process automated and more uniform:

* It can be run fully automated or in two steps to allow for manual edits of the relase notes.
* It supports both patch and full releases.
* It fetches author, issue, repo info. etc. for the release notes from GitHub.
* The file names produced are mainly the same as before, but we no use tar.gz as archive for all Unix versions.
* There isn't a fully automated CI setup in place yet, but the release tag is marked in the commit message with "[ci deploy]"

Fixes #3358

docs/layouts/section/release-notes.html

@@ -0,0 +1,6 @@
+{{ define "main" }}
+{{ range .Pages }}
+<h1>{{ .Title }} {{ .Date.Format "Jan 2, 2006" }}</h1>
+{{ .Content }}
+{{ end }}
+{{ end }}