public static Optional<String> getMainClass(String content) {
		Matcher pc = publicClassPattern.matcher(content);

		if (pc.find()) {
			return Optional.ofNullable(pc.group(1));
		} else {
			return Optional.ofNullable(null);
		}
	}
Runs the given command + arguments and returns its output (both stdout and
stderr) as a string

@param cmd The command to execute
@return The output of the command or null if anything went wrong
src/main/java/dev/jbang/util/Util.java