public static Configuration instance() {
		if (global == null) {
			String cfgFileName = System.getenv("JBANG_CONFIG");
			if (cfgFileName != null) {
				Path cfgFile = Util.getCwd().resolve(cfgFileName);
				if (Files.isReadable(cfgFile)) {
					global = get(cfgFile);
				} else {
					global = defaults().clone();
				}
			} else {
				global = Configuration.getMerged();
			}
		}
		return global;
	}
Returns a cached Configuration read from the any config files that were found
in the current environment. The `JBANG_CONFIG` environment variable can be
used to override the normal lookup process. If in that case the file can't be
found only the default values will be returned.

@return a Configuration object
src/main/java/dev/jbang/Configuration.java