RFR: Get agreement before PR

[Jesper Wilhelmsson]

Added a note on getting proper agreement on a change before creating a PR for it.

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Commit messages:
 - Get agreement before PR

Changes: https://git.openjdk.org/guide/pull/150/files
  Webrev: https://webrevs.openjdk.org/?repo=guide&pr=150&range=00
  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/guide/pull/150.diff
  Fetch: git fetch https://git.openjdk.org/guide.git pull/150/head:pull/150

PR: https://git.openjdk.org/guide/pull/150