Merge pull request #2664

Add PR template.

.github/pull_request_template.md

@@ -0,0 +1,14 @@
+<!--
+Thanks for contributing! Reminders:
++ TARGET the earliest branch where you want the change
+    3.6-dev -> 3.6.8 (bugs only)
+    3.7-dev -> 3.7.3 (non-breaking)
+    master  -> 4.0.0
++ Committers will MERGE the PR forward to newer versions
++ ADD entry to the CHANGELOG.asciidoc for the targeted version
+    Do not reference a JIRA number there
++ ADD JIRA number to title and link in description
++ PRs requires 3 +1s from committers OR
+               1 +1 and 7 day wait to merge.
++ MORE details: https://s.apache.org/rtnal
+-->