[REQ] Add a (GH-compliant) license file

[MarcoRavich]

Hi there, 1st of all thanks for this awesome work !

Since we've 'doxed' it in our HyMPS project (under AUDIO resources \ Visualization/Analysis \ Metering), can you please add a license file for it ?

Although it may sounds like a minor aspect, license file omission obviously causes an inconsistent generation of the relative badge too:

(badge-generator URL: https://badgen.net/github/license/klangfreund/LUFSMeter)

You can easily set a standardized one through the GH's license wizard tool.

Last but not least, let us know how we could improve - in your opinion - our categorizations and links to resources in order to favor collaboration between developers (and therefore evolution) of listed projects.

Hope that helps/inspires !