Update SDK constraint to <4.0.0

Bump release version

Add GitHub Actions for testing

Update CHANGELOG.md

Use enhanced enums

Use lints instead of pedantic

Requires Dart SDK >= 2.17

Bump test from 1.17.9 to 1.24.2

Bump equatable from 2.0.3 to 2.0.5

Requires Dart SDK >= 2.14

Update copyright year

Versionar para 0.3.0

Suporte a Null Safety

Criar a propriedade "Cube.prettyDefinition"

Adicionar mais dois padrões pré-definidos