Add support for yaml files

Currently, there are a myriad of services that employ yaml scripts to configure their offering. Among them, to name a few, there's Docker and CICD pipelines such as GitLab and CircleCI.

Nowadays, when a user tries to use Qt Creator open one of those config files (say, to edit a CICD pipeline or to tweak a Dockerfile) the user is forced to open these files as plaintext files, which causes problems regarding indentation and UX-wise leaves much to be desided.

It would be nice if Qt Creator enabled users to support yaml files, both to edit and reindent. Additionally, it would be nice if Qt Creator enabled users to specify yaml settings per-project.