PULL_REQUEST_TEMPLATE

#### What is this PR for?
<State the context and the changes>

#### Who should review this PR?
<State the Git users you would like to review the PR>

#### Questions:
- [ ] All unit tests executed successfully in CI environment
- [ ] Related tests executed successfully in CI environment
- [ ] Documentation updated accordingly [e.g. Readme.md, Contributing.md]
- [ ] PR ready for merging