added auto-generated architecture docs and mental model

[rdmueller]

[bmarwell]

Wow, that's too much to review on phone (Browser only shows first file, app doesn't have a search button).

I would like to read more about the rendering model. There's like no documentation about it. What goes in HOW, and how does it get accessible in the model? E.g. asciidoc's :jbake-something: is accessible in fteemarker as..? What is accessible by default?

What I read so far looks really good! OrientDB, pipeline, etc... Can't wait for Java 8+ features, better 17!

[jonbullock]

Documentation about metadata in content files, rendering model etc is here: https://jbake.org/docs/2.6.7/