Rename config.yml to hugo.yml

[coliff]

Description

hugo.yml is now recommended (over the generic sounding config.yml) as the default config based filename.
REF: https://gohugo.io/getting-started/configuration/#hugotoml-vs-configtoml

(This change isn't important, feel free to close if you'd rather use config.yml for any reason)

Motivation & Context

Changing this may make it easier for code editors and build tools to identify this as a Hugo configuration file and project.

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would change existing functionality)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using npm run lint)
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

Live previews

• https://deploy-preview-{your_pr_number}--twbs-bootstrap.netlify.app/

Related issues

[julien-deramond]

Thanks for the PR @coliff
On my side, I don't mind the change if it is the recommended way :)
There's probably a change to do in generate-sri.js as well.
@XhmikosR You have more experience than me with Hugo. Thoughts about this change?