Look up config file in parents recursively

[qwtel]

Use case: I add categories to posts by putting them into folders of the same name (Jekyll supports this!), e.g.

├── jekyll
│   └── update
│       └── _posts
│           └── 2019-04-07-welcome-to-jekyll.md

Instead of adding an option to Jekyll Compose, I think the more unix-y way of adding support for this just cding into jekyll/update and running draft, publish, etc. commands there.

However, Jekyll Compose can't locate the config file in this case, as it's only looking in the current working directory. Support for recursive search until it finds a config file in a parent would enable this.