refactor: remove usage of mixin on error classes

[almeidx]

Please describe the changes this PR makes and why it should be merged:
Removed the internal mixin function DiscordjsErrorMixin in order to provide better documentation
https://discord.js.org/docs/packages/discord.js/14.14.1/DiscordjsError:Class

Status and versioning classification:

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

2 Ignored Deployments

Name	Status	Preview	Updated (UTC)
discord-js	⬜️ Ignored (Inspect)		Feb 13, 2024 11:35am
discord-js-guide	⬜️ Ignored (Inspect)		Feb 13, 2024 11:35am

[ssilve1989]

Why did the constructor become private on the typings? A private constructor would imply some other way of creating the object, via some static method, but the internal code still creates it via new. This change to making the constructor private breaks matching on instance type with tools like ts-pattern.

Ex.

    match(error)
      .with(
        P.instanceOf(DiscordjsError),
        ({ code }) => code === DiscordjsErrorCodes.InteractionCollectorError,
        () => { /* some handler code */ }
      )

now breaks with

Argument of type 'typeof DiscordjsError' is not assignable to parameter of type 'AnyConstructor'.
Cannot assign a 'private' constructor type to a 'public' constructor type.