add a license

[vbatts]

hey hey,

can this project add a LICENSE/COPYING, or even a blurb in the README if it defers to the project license (https://github.com/flatpak/flatpak/blob/master/COPYING)?

[mwleeds]

docs.flatpak.org says at the bottom "Licensed under Creative Commons Attribution 4.0 International License" so perhaps it would make sense to use that here too.

Pretty sure @allanday and @jimmac are the main copyright holders based on the commit history

[jimmac]

Sounds fine with me.

[mwleeds]

Actually CC recommends not to use their licenses for software so we can use it for the content of the site but we would still need a license for the software.

[razzeee]

I think it would be good, to get a license in place