RFR: Describe in JBS before PR

[Jesper Wilhelmsson]

Added a note to remind to have a description in JBS before creating a PR.

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Commit messages:
 - Describe in JBS before PR

Changes: https://git.openjdk.org/guide/pull/141/files
  Webrev: https://webrevs.openjdk.org/?repo=guide&pr=141&range=00
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/guide/pull/141.diff
  Fetch: git fetch https://git.openjdk.org/guide.git pull/141/head:pull/141

PR: https://git.openjdk.org/guide/pull/141