Add pull request template to Contile

[data-sync-user]

In order to promote quality and meet Github recommended community standards, add a pull request template to the Contile project.

Resources

• Github - Creating a pull request template for you repository

Examples

• fxa template
• firefox-ios
  • template
  • Pull Request Naming Guide
• firefox-android template
• experimenter template
• blurts-server template

┆Issue is synchronized with this Jira Task
┆Epic: Contile: maintenance