restish: update to 0.18.0.

This release brings a few important changes worth calling out:

    Freedesktop conventions are now followed, meaning the location
    of configuration and cache files is now operating-system
    dependent. Files are automatically moved over when running the
    new Restish release. The new restish api edit command makes it
    easy to edit your API configuration, which will now be located:

        Mac: ~/Library/Application Support/restish/apis.json
        Linux: ~/.config/restish/apis.json
        Windows: %AppData%\restish\apis.json

    If no OpenAPI server locations match, the default operation
    base path is now the path component of the base configuration
    value. This can be overridden via the operation_base parameter.
    See docs at https://rest.sh/#/configuration?id=operation-base-path

    Local and remote references are now supported in OpenAPI,
    including relative refs with the base set to the location of
    the OpenAPI file. Restish can now officially load the DigitalOcean
    API spec.

(wiz)