workflow: add a default template for Merge Request
Introduce a first basic template to try the feature.
---
name: Official Review
about: Submit a series for review
---
/assign_reviewer @mercurial.review
Welcome to the Mercurial Merge Request creation process:
* Set a simple title for your MR,
* All important information should be contained in your changesets' content or description,
* You can add some workflow-relevant information here (eg: when this depends on another MR),
* If your changes are not ready for review yet, click `Start the title with Draft:` under the title.
More details here:
* https://www.mercurial-scm.org/wiki/ContributingChanges
* https://www.mercurial-scm.org/wiki/Heptapod