Added pull request description

Author: sonamtenzin2

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,14 @@
+## Description
+<!-- Provide a summary of what the PR does and why it is being submitted. -->
+
+## Testing
+<!-- Describe how the changes have been tested. Provide test instructions or details. -->
+
+## External links
+<!-- Any related external links can be added here -->
+
+- [JIRA](https://hashicorp.atlassian.net/browse/xxxx)
+- [RFC](https://docs.google.com/document/d/xxxx)
+- [PRD](https://docs.google.com/document/d/xxxx)
+- [Related PR](https://github.com/hashicorp/atlas/pull/xxxx)
+- [Documentation](https://github.com/hashicorp/terraform-docs-common/pull/xxxx)