RFR: 253: Add note about git-publish to README

[Erik Helin]

Hi all,

please review this small patch that updates the README with some info about
`git-publish`.

Thanks,
Erik

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Commits:
 - 2dce21e2: Update the README

Changes: https://git.openjdk.java.net/skara/pull/390/files
 Webrev: https://webrevs.openjdk.java.net/skara/390/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-253
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/skara/pull/390.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/390/head:pull/390

PR: https://git.openjdk.java.net/skara/pull/390