add default merge request template

Add the following MR template:

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Summary

Description about the changes and what it is supposed to accomplish (screenshot, gifs are also welcome 👍).
Any guidance for the reviewer: what to look at, where to start, risks ... this can also be done by adding comments to your own changes.

Type of change

Select which apply, or delete options that are not relevant.

• 💡 New feature
• 🐛 Bug fix
• 🔧 Refactoring that neither fixes a bug nor adds a feature
• 🚀 Performance improvement
• ✅ Test: adding missing or correcting existing tests
• 😒 chore/pipeline/CI/third party upgrade
• 🔒 Security fix
• 📃 Documentation
• 😎 Style, formatting, fix typo ...
• ❗ Deprecation
• 🔚 Removing a functionality

Validation

Select which apply, add any description how code has been validated. At least one method must be provided!

• New tests added
• Covered by the unit tests
• Covered by the integration tests
• Non functional testing (performance, scalability, security ...)
• Manual testing, description:

Special matter

Delete options that are not relevant. If one of them apply, please ensure to assign it to appropriate reviewers and that enough details are provided.
Change may require additional specific focus and/or reviewers:

• ⚠ Breaking change: must ensure to be well understood and communicated.
• 💥 Security: e.g. changes touch sensitive part of the code, changes resource access (cache), changes in the data flow ...
• 🆕 New dependency: changes add one or more dependencies.

Work Item

• Work item link provided: