Add LICENSE file

[icaoberg]

1. Download this file https://www.gnu.org/licenses/gpl-3.0.txt.
2. Rename to LICENSE
3. Upload file to main folder.

[Eunice-Son]

Do you want me to add the file to braininventory folder?

[icaoberg]

@Eunice-Son add it to the top folder of the project. No braininventory. One level up. Do it by tomorrow.