RFR: More information on fix version usage

[Jesper Wilhelmsson]

Added more information on how to set fix version when closing an issue.
Also fixed some broken links.

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Commit messages:
 - Fixed linebreaks
 - More information on fix version usage

Changes: https://git.openjdk.org/guide/pull/128/files
  Webrev: https://webrevs.openjdk.org/?repo=guide&pr=128&range=00
  Stats: 47 lines in 3 files changed: 22 ins; 0 del; 25 mod
  Patch: https://git.openjdk.org/guide/pull/128.diff
  Fetch: git fetch https://git.openjdk.org/guide.git pull/128/head:pull/128

PR: https://git.openjdk.org/guide/pull/128