Jekyll config requires .yml, not .yaml
I encountered a peculiar issue with GitHub’s Pages’ Jekyll handling recently.
The config file must be _config.yml, not _config.yaml.
Until recently, GitHub accepted both, even though the documentation gives the
.yml extension. This means if you were using .yaml for some reason, your blog
would break and revert to default settings.
Without a valid settings file, GitHub Pages will still build Jekyll pages without an error, but the blog would lose its custom configuration.