Add required fields to templates

[miguelbalparda]

Description

Developers submit PRs and issues without the template. This PR adds required fields.

Fixed Issues (if relevant)

1. Not relevant

Manual testing scenarios

1. Create a PR or issue
2. New text reads "Fields marked with (*) are required. Please don't remove the template."

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[ihor-sviziev]

@sidolov will it be correctly validated by engcom bot?

[magento-engcom-team]

@miguelbalparda thank you for contributing. Please accept Community Contributors team invitation here to gain extended permissions for this repository.

[sidolov]

@ihor-sviziev it should work correctly with such changes, but we need to verify after the PR will be merged.

[magento-engcom-team]

Hi @miguelbalparda. Thank you for your contribution.
We will aim to release these changes as part of 2.3.1.
Please check the release notes for final confirmation.