6-licensediff command

This example demonstrates loading two SPDX tag-value files from disk into memory, and generating a diff of the concluded licenses for Files in Packages with matching IDs in each document. This is generally only useful when run with two SPDX documents that describe licenses for subsequent versions of the same set of files, AND if they have the same identifier in both documents. Run project: go run example_licensediff.go ../sample-docs/tv/hello.spdx ../sample-docs/tv/hello-modified.spdx