RFR: SKARA-1119: A bot should remind a PR author not to force push

[Guoxiong Li]

Hi all,

This patch adds a suggestion comment to the PR when the developers force-push the branch each time. Because I can't find the related rest api of the GitLab so I only implement it for GitHub.

Thanks for taking the time to review.

Best Regards,
-- Guoxiong

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Commit messages:
 - SKARA-1119: A bot should remind a PR author not to force push

Changes: https://git.openjdk.java.net/skara/pull/1328/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1328&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-1119
  Stats: 163 lines in 9 files changed: 159 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/skara/pull/1328.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1328/head:pull/1328

PR: https://git.openjdk.java.net/skara/pull/1328