ICU-21480 Update GitHub pull request template: JIRA issue number is needed on commit messages.
diff --git a/.github/pull_request_template.md b/.github/pull_request_template.md
index 9386c06..c8a1010 100644
--- a/.github/pull_request_template.md
+++ b/.github/pull_request_template.md
@@ -1,18 +1,20 @@
<!--
-Thank you for your pull request.
+Thank you for your pull request!
+
Please see http://site.icu-project.org/processes/contribute for general
information on contributing to ICU.
-You will be automatically asked to sign the contributors license before the PR is accepted.
+You will be automatically asked to sign the contributors license agreement (CLA) before the PR is accepted.
- sign: https://cla-assistant.io/unicode-org/icu
- license: http://www.unicode.org/copyright.html
-->
##### Checklist
-- [ ] Issue filed: https://unicode-org.atlassian.net/browse/ICU-_____
-- [ ] Updated PR title and link in previous line to include Issue number
-- [ ] Issue accepted
-- [ ] Tests included
-- [ ] Documentation is changed or added
-
+- [ ] Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-_____
+- [ ] Required: The PR title must be prefixed with a JIRA Issue number. For example: "ICU-1234 Fix xyz"
+- [ ] Required: The PR description must include the link to the Jira Issue, for example by completing the URL in the first checklist item
+- [ ] Required: Each commit message must be prefixed with a JIRA Issue number. For example: "ICU-1234 Fix xyz"
+- [ ] Issue accepted (done by Technical Committee after discussion)
+- [ ] Tests included, if applicable
+- [ ] API docs and/or User Guide docs changed or added, if applicable
