Rethinking the default class hierarchy: Milestone 1, Week 2

[Robert Aron]

[Project 
description](https://gist.github.com/edi33416/0e592f4afbeb2fb81d3abf235b9732ce)
[SAOC 
projects](https://dlang.org/blog/2021/08/30/saoc-2021-projects/)

Hello!

Last week I managed to do the following tasks for #SAOC2021:
- read about how Rust handles this; it has a totally different 
approach: data aggregates (structs, enums and tuples) are all 
unrelated types. You can define methods on them, and make the 
data itself private, all the usual tactics of encapsulation, but 
there is no subtyping and no inheritance of data.
- started to write the DIP

The plan for the next week:
- continue to write the DIP and ask mentors for review
- take a look at the code Edi wrote for his talk