LF AI & Data Blog Guidelines - Update/Revise/Vet

[NSouthernLF]

https://github.com/lfai/foundation/blob/main/blog-guidelines.md

These need to be reviewed and edited by the current marketing team to ensure compliance with current LF policy - and the edited version should be placed in markdown on the Github, replacing the above file. The Google Drive version, as a duplicate, can likely be deleted.