feat: Waku API's subscribe

[fryorcraken]

Introduced a new subscribe function to the Waku API.

Problem / Description

Developer need a simple API to receive messages.

Solution

See TODOs / Notes

API

interface IMessageEmitterEvents {
  [contentTopic: string]: CustomEvent<Uint8Array>;
}

interface IWaku {
	messageEmitter: TypedEventEmitter<IMessageEmitterEvents>;
	subscribe(contentTopics: ContentTopic[]): void;
}

Usage

const contentTopic = "/some/0/content-topic/proto"

// Setup event listener for messages
waku.messageEmitter.addEventListener(contentTopic, (event) => {
	const payload:UInt8Array = event.detail;
	// process payload
  });
});

// Setup event listener for errors
waku.events.addEventListener("error:subscribe", (event) => {
	console.log("internal error:", event.detail);
  });
});

// trigger node subscription
waku.subscribe([contentTopic]);

TODOs / Notes

Specs: waku-org/specs#86

• Remove callback in favour of event emission
• Demonstrate integration with encryption
• Demonstrate integration with encryption and reliable channels

Related to #2216

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Checklist

• Code changes are covered by unit tests.
• Code changes are covered by e2e tests, if applicable.
• Dogfooding has been performed, if feasible.
• A test version has been published, if required.
• All CI checks pass successfully.