[Feature Request] Interfaces and Implementors

Nadie ha tomado este issue todavía.

The current class system is alright, but imagine this: I have a `Stream` class which is extended by `ReadStream`, `WriteStream`, `SeekableStream`, etc.
```lua
---@class Stream
---@field close fun() Deallocates or hangs up a stream.

---@class SeekableStream: Stream
---@field seek fun(whence: SeekWhence, offset: integer): integer

---@class ReadStream: Stream
---@field read fun(self: ReadStream, length: integer): string|nil

---@class WriteStream: Stream
---@field write fun(data: string): integer

---@class StringStream: ReadStream, SeekableStream Streams data out of a string.
```
Now I have a function which takes any Seekable, Readable string. How do I specify this? Either we need a conjunction type (`ReadStream & SeekableStream`, which has keys from both), or we need (preferably) interfaces, which are generic and can be extended by classes. The reason I suggest interfaces is because if I write this:
```lua
---@param length integer
---@return string|nil
function StringStream:read(length)
if self.buffer == nil then
error("Stream is closed", 2)
end
if self.cursor > #self.buffer then
return nil
end
local out = string.sub(self.buffer, self.cursor, math.min(#self.buffer, self.cursor + length))
self.cursor = self.cursor + #out
return out
end
```
and I omit the type annotation, it assumes `read` is already defined because `StringStream` extends `ReadStream`, and it doesn't validate types (arguments and return type are `any`).

Comienza con el comportamiento de la herencia de clases y las anotaciones de tipos descrito en el issue, incluidos los ejemplos de Stream, ReadStream, SeekableStream y StringStream. Compara los enfoques propuestos de tipo de conjunción y de interfaces, y luego verifica que las anotaciones de métodos heredadas sigan validando los argumentos y los tipos de retorno cuando las implementaciones omiten sus propias anotaciones.

Escrito por el modelo de indexación a partir del texto del issue.