RFR: cover the documentation linking options in release notes

[Roger Calnan]

added an explanation on the support of JavaDoc like links and the automatic linking of JBS IDs

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Commit messages:
 - adjust case of text in section headings
 - cover the documentation linking options in release notes

Changes: https://git.openjdk.org/guide/pull/167/files
  Webrev: https://webrevs.openjdk.org/?repo=guide&pr=167&range=00
  Stats: 25 lines in 2 files changed: 24 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/guide/pull/167.diff
  Fetch: git fetch https://git.openjdk.org/guide.git pull/167/head:pull/167

PR: https://git.openjdk.org/guide/pull/167