[ServiceWorker] Add verbose mode for debugging (mlc-ai#410)

Using service worker sometimes is tricky, especially when you are trying
to debug an issue. This PR adds additional `debug` level logs for
printing the entire event trace for easier debugging.

Broswer console in default logging level:
<img width="876" alt="Screenshot 2024-05-22 at 7 51 22 PM"
src="https://github.com/mlc-ai/web-llm/assets/23090573/dfc4b477-0e5e-4bb7-abd7-773b045043f4">

Broswer console in verbose logging level:
<img width="878" alt="Screenshot 2024-05-22 at 7 51 48 PM"
src="https://github.com/mlc-ai/web-llm/assets/23090573/47d085ad-a584-4ffa-890d-07ab892f1e67">

.prettierrc

@@ -0,0 +1,3 @@
+{
+  "trailingComma": "all"
+}

src/service_worker.ts

@@ -1,5 +1,5 @@
 import * as tvmjs from "tvmjs";
-import { AppConfig, ChatOptions, MLCEngineConfig, ModelRecord } from "./config";
+import { AppConfig, ChatOptions, MLCEngineConfig } from "./config";
 import { ReloadParams, WorkerRequest, WorkerResponse } from "./message";
 import { MLCEngineInterface, InitProgressReport } from "./types";
 import {
@@ -40,7 +40,7 @@ export class ServiceWorkerMLCEngineHandler extends MLCEngineWorkerHandler {
   >();
   private initReuqestUuid?: string;
 
-  constructor(engine: MLCEngineInterface, verbose = false) {
+  constructor(engine: MLCEngineInterface) {
     if (!self || !("addEventListener" in self)) {
       throw new Error(
         "ServiceWorkerGlobalScope is not defined. ServiceWorkerMLCEngineHandler must be created in service worker script.",
@@ -90,6 +90,9 @@ export class ServiceWorkerMLCEngineHandler extends MLCEngineWorkerHandler {
     onError?: () => void,
   ): void {
     const msg = event.data as WorkerRequest;
+    console.debug(
+      `ServiceWorker message: [${msg.kind}] ${JSON.stringify(msg.content)}`,
+    );
 
     if (msg.kind === "keepAlive") {
       const reply: WorkerRequest = {
@@ -212,7 +215,7 @@ export async function CreateServiceWorkerMLCEngine(
 export class ServiceWorkerMLCEngine extends WebWorkerMLCEngine {
   missedHeatbeat = 0;
 
-  constructor(worker: IServiceWorker, keepAliveMs = 10000, verbose = false) {
+  constructor(worker: IServiceWorker, keepAliveMs = 10000) {
     if (!("serviceWorker" in navigator)) {
       throw new Error("Service worker API is not available");
     }
@@ -223,6 +226,9 @@ export class ServiceWorkerMLCEngine extends WebWorkerMLCEngine {
       "message",
       (event: MessageEvent) => {
         const msg = event.data;
+        console.debug(
+          `MLC client message: [${msg.kind}] ${JSON.stringify(msg.content)}`,
+        );
         try {
           if (msg.kind === "heartbeat") {
             this.missedHeatbeat = 0;
@@ -241,6 +247,7 @@ export class ServiceWorkerMLCEngine extends WebWorkerMLCEngine {
     setInterval(() => {
       this.worker.postMessage({ kind: "keepAlive", uuid: crypto.randomUUID() });
       this.missedHeatbeat += 1;
+      console.debug("missedHeatbeat", this.missedHeatbeat);
     }, keepAliveMs);
   }