Develop how natural-earth, fonts and sprites assets are built #101
Description
While we do have details in the README about how everything which needs regular update is built / retrieved, we do miss details about natural-earth, fonts and sprites packages.
This is not a deal breaker because we (generally) never update these assets, but should something goes wrong / need to be tweaked, it would help to know how these files were built originally. Does not need to be automated, but at least some written instructions would help.
Or did I simply missed these details in the documentation?