feat(licensing): add missing license for demo

Even if it is a private package,
a license is usefull,
because code may be copied and pasted.
We used LGPLv3+ because it is used in other packages,
so like this it is the same for all packages,
but we may use a non-copyleft license for this specific package,
like Creative Commons 0 version 1.0
(https://www.gnu.org/licenses/license-list.en.html#CC0)
or GNU All-Permissive License
(https://www.gnu.org/licenses/license-list.en.html#GNUAllPermissive).