Add default issue and MR templates

What does this merge request do and why?

This MR adds a default issue and merge request template for this repository. This will:

• Prompt the creator to provide much needed information to facilitate smooth review
• Label the issue and merge request accordingly (with quick action)

How to set up and validate locally

This can only be verified after merged. Once it is merged, these two templates will be automatically populated.

Merge request checklist

• [-] Tests added for new functionality. If not, please raise an issue to follow-up.
• [-] Documentation added/updated, if needed.