Request: Datapack guide & template datapack (Java)

First off, thank you for implementing datapacks. They look like they are very powerful things that will be great for the community. There is only one problem: Inaccessibility and incomprehensibility.

I was quite comfortable making custom worlds back with the old "pages of sliders" system, and I have done some xml and java stuff. But figuring out how to make even a basic datapack to change the most minuscule detail about world-gen has an unacceptably steep learning curve.

For example, it took over a week (10+ hours) to make a datapack that increased coal spawn up to 30. That's it, just to change one variable. And then another 5 to get that change into a datapack. Now that I know how to do it, it is extremely easy. The problem is that there is no information available for it. I had to use info on at least six different websites and some direct instruction from random people on discord just to figure out how to change that one variable. For an officially supported feature, this is terrible.

What would be extremely valuable to the community would be to have a fully documented guide to what everything in the datapack means, and a *current vanilla* worldgen datapack that people can look at as a template.

Summary Request:
- An official, complete, and detailed guide to what everything in the datapack means. (not just the default values and/or ranges)
- An official, complete, vanilla world-gen template. (preferably the complete worldgen for current vanilla world)

Thank you!