refactor: add autocomplete for ExchangeType

[mephju]

No description provided.

[ThomasSarlin]

Looks good to me,

[carlhoerberg]

eslint didn't like this:

/home/runner/work/amqp-client.js/amqp-client.js/src/amqp-channel.ts
  866:81  error  Don't use `{}` as a type. `{}` actually means "any non-nullish value".
- If you want a type meaning "any object", you probably want `object` instead.
- If you want a type meaning "any value", you probably want `unknown` instead.
- If you want a type meaning "empty object", you probably want `Record<string, never>` instead.
- If you really want a type meaning "any non-nullish value", you probably want `NonNullable<unknown>` instead  @typescript-eslint/ban-types

what was your intention @mephju? I don't see how this "adds autocompletetion".

[mephju]

Hello @carlhoerberg

It's a well known TS trick to workaround the issue that literal strings are also assignable to string (which is the reason for lack of autocomplete).
With this trick you get the autocomplete for the union but you are still able to assign any string you like.

Please take a look here:
https://stackoverflow.com/questions/74467392/autocomplete-in-typescript-of-literal-type-and-string
and here
microsoft/TypeScript#29729