* docs: fix licensing info for generated files
* change generate_cvss_enums.go to note that the input file is
relevant for the license.
* change license and copyright of cvss20enums.go and cvss3enums.go
to BSD-3-Clause and FIRST.
* add reuse.software 3.0 compatible files for the schema cvss files.
* Stamp right license into generated files.
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Co-authored-by: Sascha L. Teichmann <sascha.teichmann@intevation.de>