Add support for fetching room messages

[tadzik]

Is your feature request related to a problem? Please describe.

There is currently no wrapper around https://spec.matrix.org/v1.3/client-server-api/#get_matrixclientv3roomsroomidmessages to be able to load messages from a room.

Describe the solution you'd like

A nicely typed wrapper for that endpoint.

Describe alternatives you've considered

I'm currently doing this manually with doRequest but it's a bit of extra legwork that I'd rather not do:

        let from: string|undefined;
        for (;;) {
            const events = await this.matrixClient.doRequest(
                'GET',
                `/_matrix/client/v3/rooms/${encodeURIComponent(roomId)}/messages`,
                { dir: 'b', limit: 100, from },
            );
            for (const ev of events.chunk) {
                if (ev.type === 'm.room.create') {
                    break;
                } else if (ev.type === interestingEventType) {
                    interestingEvents.push(ev.content);
                }
            }
            if (from === events.end) break;
            from = events.end;
        }
        // use interestingEvents

The above could serve as an inspiration for the PR.

[AndrewKvalheim]

I ended up adding an async generator with token management hidden from the public interface:

const pages = client.getRoomEvents(room, "reverse", { types: ["m.reaction"] });

for await (const page of pages) {
  for (const reaction of page) {
    console.log(reaction);
  }
}