RFR: Section on release notes [v7]

[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 four additional commits since the last revision:

 - Update src/index.md
   
   Co-authored-by: calnan <69008917+calnan at users.noreply.github.com>
 - Update src/index.md
   
   Co-authored-by: calnan <69008917+calnan at users.noreply.github.com>
 - Update src/index.md
   
   Co-authored-by: calnan <69008917+calnan at users.noreply.github.com>
 - Update src/index.md
   
   Co-authored-by: calnan <69008917+calnan at users.noreply.github.com>

-------------

Changes:
  - all: https://git.openjdk.java.net/guide/pull/75/files
  - new: https://git.openjdk.java.net/guide/pull/75/files/6394ea02..d401bcda

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=guide&pr=75&range=06
 - incr: https://webrevs.openjdk.java.net/?repo=guide&pr=75&range=05-06

  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 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