[8.14](backport #3985) Add license (#3988)

* Add license (#3985)

(cherry picked from commit d48f0cb)

# Conflicts:
#	README.md

* Update README.md

---------

Co-authored-by: Lisa Cawley <lcawley@elastic.co>
Co-authored-by: Brandon Morelli <brandon.morelli@elastic.co>

Author: 3 people