update license format of web-animations, use SPDX
update license format of web-animations, use SPDX

cc @samthor

dhenson02/cdnjs,viskin/cdnjs,viskin/cdnjs,viskin/cdnjs,viskin/cdnjs,dhenson02/cdnjs,dhenson02/cdnjs,viskin/cdnjs,dhenson02/cdnjs