parse also *.yml file suffix as YAML; closes #1958

[bast]

previously only files with *.yaml suffix were recognized as YAML

Questions to the reviewer:

• Should I add more to the documentation?
• Should I add anything to the changelog or change commit message format?
• I have only tested this locally with load_data from a path ending with *.yml (and this worked). Should I add/extend some test?
• I tried to also test this for URLs but I am unsure how the parsing works there. It does not seem to look at the URL suffix (tested with .toml and .yaml) but perhaps at the header. So I am unsure whether more is needed for URLs or whether they already worked and I did not have a good test. I tried with pages served via https://raw.githubusercontent.com/ but maybe they had wrong header.

Sanity checks:

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Are you doing the PR on the next branch?
• Have you created/updated the relevant documentation page(s)?

[Keats]

I believe load_data with urls will basically require you to be explicit about the format you're loading rather than relying on headers. I'll double-check tomorrow.

No need to add tests, it's just a simple match.

[Keats]

Yep, it looks like it just defaults to Plain for urls

[bast]

Thanks for double-checking it. And the setting makes sense.