di-edid-decode: help message for the executable

As an end user I was trying to test this library (libdisplay-info), however I wasn't sure on how to execute the provided binary (di-edid-decode) and felt the need of help message or usage options to be able to execute it. With this, initially I just wanted to come up with an aperture for help message or usage, which can extended based on your feedbacks. Though I'm unsure whether this is needed, but at least this help message seems useful for the newbies'.