RFR: Section on release notes [v6]

[Jesper Wilhelmsson]

> The meat of the procedure here was inspired by Daniel Fuchs' comment in JDK-8273727.
> [[JDK-8273727] (prop) Canonical property storage - Java Bug System](https://bugs.openjdk.java.net/browse/JDK-8273727?focusedCommentId=14448738&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14448738)

Jesper Wilhelmsson has updated the pull request incrementally with one additional commit since the last revision:

  Rewritten and added more info.

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Changes:
  - all: https://git.openjdk.java.net/guide/pull/75/files
  - new: https://git.openjdk.java.net/guide/pull/75/files/e4a4b604..6394ea02

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=guide&pr=75&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=guide&pr=75&range=04-05

  Stats: 113 lines in 2 files changed: 78 ins; 1 del; 34 mod
  Patch: https://git.openjdk.java.net/guide/pull/75.diff
  Fetch: git fetch https://git.openjdk.java.net/guide pull/75/head:pull/75

PR: https://git.openjdk.java.net/guide/pull/75