RFR: 290: Goodies to help keeping the fork up2date

[Mario Torre]

add git-sync to the README

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Commits:
 - f2bfacf4: add git-sync to the README

Changes: https://git.openjdk.java.net/skara/pull/481/files
 Webrev: https://webrevs.openjdk.java.net/skara/481/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-290
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/skara/pull/481.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/481/head:pull/481

PR: https://git.openjdk.java.net/skara/pull/481