Gleam patterns documented

[lpil]

If you have experience with OOP or some other non-functional paradigm then it may be unclear how to write your code. Documenting common design patterns would be helpful!

An existing one for Haskell: https://kowainik.github.io/posts/haskell-mini-patterns

What should we cover?

• Tail calls with an accumulator
• Making invalid states unrepresentable
• Result error wrapping
• The builder pattern
• Opaque types and smart constructors
• Phantom types
• ???