v0.4.0

• breaking: the update to lume/variable requires always using class decorators now (f.e. @reactive class {...} or @element class extends Element {...}), otherwise reactivity won't work in some build setups depending on whether the user's setup has the new class fields semantics or not ([[Define]] vs [[Set]] semantics). New tests have been added to ensure that decorators work in every build config permutation (TypeScript decorators with or without useDefineForClassFields, and Babel legacy or non-legacy decorators with or without loose mode for class properties)
• This fixes some edge case bugs too