Improve attribution by adding the license files locally.

[diegoreymendez]

Resolves some of the concerns raised in #864 .

• Adds the license files from the 3rd party open source projects we're using.
• Updates README.md to point to the local copies of those files.

Please keep in mind the file names are exactly as they were in their original projects so they may look slightly inconsistent.

[astralbodies]

:shipit:

Thanks for that!

[diegoreymendez]

Ty @astralbodies !