📝 Add new docs section, How To - Recipes, move docs that don't have to be read by everyone to How To (fastapi#10114)

* 📝 Start How To docs section, move Peewee, remove Peewee from dependencies

* 🚚 Move em files to new locations

* 🚚 Move and re-structure advanced docs, move relevant to How To

* 🔧 Update MkDocs config, new files in How To

* 📝 Move docs for Conditional OpenAPI for Japanese to How To

* 📝 Move example source files for Extending OpenAPI into each of the new sections

* ✅ Update tests with new locations for source files

* 🔥 Remove init from Peewee examples

Author: tiangolo