Implement PR template to assist review & release

This duplicates the template used for buildah.  The intention
is to make it immediately clear to reviewers:

* The intended/basic purpose of the PR (also machine readable)
* Why are changes being proposed
* If there are any specific items need additional checking or scrutiny
* What should go into the release-notes (if anything).

Signed-off-by: Chris Evich <cevich@redhat.com>

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,7 +1,41 @@
 <!--
 Thanks for sending a pull request!
 
-Please make sure you've read our contributing guidelines and how to submit a pull request (https://github.com/containers/podman/blob/master/CONTRIBUTING.md#submitting-pull-requests).
+Please make sure you've read our contributing guidelines and how to submit a pull request (https://github.com/containers/podman/blob/main/CONTRIBUTING.md#submitting-pull-requests).
 
 In case you're only changing docs, make sure to prefix the pull-request title with "[CI:DOCS]".  That will prevent functional tests from running and save time and energy.
+
+Finally, be sure to sign commits with your real name.  Since by opening
+a PR you already have commits, you can add signatures if needed with
+something like `git commit -s --amend`.
 -->
+
+#### What this PR does / why we need it:
+
+<!---
+Please put your overall PR description here
+-->
+
+#### How to verify it
+
+<!---
+Please specify the precise conditions and/or the specific test(s) which must pass.
+-->
+
+#### Which issue(s) this PR fixes:
+
+<!--
+Please uncomment this block and include only one of the following on a
+line by itself:
+
+None
+
+-OR-
+
+Fixes #<issue number>
+
+*** Please also put 'Fixes #' in the commit and PR description***
+
+-->
+
+#### Special notes for your reviewer: