.github: Add PR template

Author: lilic

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,19 @@
+<!--
+
+Before making a PR, please read our contributing guidelines https://github.com/operator-framework/operator-sdk/blob/master/CONTRIBUTING.MD
+
+Note: Make sure your branch is rebased to the latest upstream master.
+
+--!>
+
+**Description of the change:**
+
+
+**Motivation for the change:**
+
+<!--
+
+Note: If this PR is fixing an issue make sure to add a note saying:
+Closes #<ISSUE_NUMBER>
+
+--!>