Add configuration support

[loganmzz]

Having configuration file at Crate level let's minimize configuration overrides required to be set on each buildable structs and their fields.

It let's override or extend defaults such as type names which are considered Default, Option or Extend (see #16). Including capacity to remove existing defaults.

Configuration format should be defined. A JSON support will be welcomed. Considered options:

Language	Rust crate	Serde support
YAML	serde_yaml	✅
Dhall	serde_dhall	✅
HCL	hcl-rs	✅
TOML	toml	✅
Pkl	#pkl	⛔
Nickel	nickel-lang-core	✅
CUE	No	⛔