Use the web standard Request/Response types for `installer.handleCallback`

Currently, the installer.handleCallback method supports the Node specific IncomingMessage and ServerResponse. This is not ideal for apps using Bun and other frameworks like Hono:

Here,

1. c.req.raw is of type Request and is not assignable to IncomingResponse which is a node:http specific type.
2. c.Res (type of Response) is not assignable to ServerResponse<IncomingMessage>.

I understand that this is node-slack-sdk and not bun-slack-sdk but this feature request is more about adopting a more compatible standard hence making it more framework/runtime agnostic. Some kind of backward compatibility might be needed.

If this is out of scope, how can I use this package with my above example (Hono and Bun)?

Packages:

Select all that apply:

• @slack/web-api
• @slack/rtm-api
• @slack/webhooks
• @slack/oauth
• @slack/socket-mode
• @slack/types
• I don't know

Requirements

Please read the Contributing guidelines and Code of Conduct before creating this issue or pull request. By submitting, you are agreeing to those rules.

The entry point is installer.handleCallback in @slack/oauth; read its current Request/Response type declarations and the linked OAuth handling documentation first. Account for both Node IncomingMessage/ServerResponse and web-standard Request/Response, then verify that the Hono/Bun example no longer has the reported type incompatibilities while preserving backward compatibility.