ORC-651: Use GitHub Pull Request Template
ORC-651: Use GitHub Pull Request Template

### What changes were proposed in this pull request?

This PR aims to add `GitHub Pull Request Template`.

### Why are the changes needed?

This will help contributors and reviewers to provide a standardized way to communicate.

### How was this patch tested?

Manually review the template.

Closes #525
apache/orc,apache/orc,omalley/orc,apache/orc,omalley/orc,apache/orc,omalley/orc,omalley/orc,apache/orc,omalley/orc,apache/orc,omalley/orc,apache/orc,omalley/orc,apache/orc