If --config <path> is a file, it will try to load that file.
If --config <directory> Browsability shall look for a .browsability.hjson file within that directory.
If --config is omitted, it will look for a config file at <project root>/.browsability.hjson and <project root>/config/.browsability.hjson.
Throws BrowsabilityError.MISSING_FILE if the file does not exist.
Throws BrowsabilityError.READ_FAILED if Browsability cannot read the file.
Throws BrowsabilityError.PARSE_FAILED if Browsability fails to parse the file (invalid hjson, or is not a type of BrowsabilityConfiguration).
If --config is omitted, and no config files were found, Browsability will run against the current directory with the default settings.