Clarification of the terms of use for the Software Heritage Graph dataset

[rdicosmo]

This issue concerns the dataset description at https://github.com/awslabs/open-data-registry/blob/main/datasets/software-heritage.yaml
Due to the recent rise in the quest of data for LLM training, we have published principles that cover this usage.
The description of the dataset must hence be updated to include them, and to make it clearer what are the general terms of use.

[rdicosmo]

#2373 adds the link to the principles for LLM
#2375 makes explicit the scope of the Creative Commons licence, and adds link to tutorial and tools

[rdicosmo]

Update #2375 to pass Yaml checks