SUPPORT file support in repository

Description

To point contributors to where they can find support, a SUPPORT file can be useful.

This was a good idea by GitHub: https://github.com/blog/2400-support-file-support

Proposal

Support this filetype by quick linking to it from the project home page and showing it when creating a new issue when it's present in the .gitlab directory of the repository.

Links / references

Documentation blurb

Overview

What is it? Why should someone use this feature? What is the underlying (business) problem? How do you use this feature?

Use cases

Who is this for? Provide one or more use cases.

Feature checklist

Make sure these are completed before closing the issue, with a link to the relevant commit.

• Feature assurance
• Documentation
• Added to features.yml