better comment explaining the need for initServiceWorker() in event handlers (ref. #31)

service-worker.js

@@ -760,7 +760,14 @@ self.addEventListener('activate', async event => {
 
 self.addEventListener('fetch', async event => {
     return void event.respondWith(async function () {
-        // initialize the SW
+        // initialize the SW; this is necessary as SW can be stopped at any time
+        // and restarted when an event gets triggered -- `fetch` is just such an event.
+        // 
+        // `install` and `activate` events only handle the initial installation of the SW
+        // this means that we might end up here without initServiceWorker() ever being run
+        // and so in a situation where plugins have never been actually set-up!
+        // 
+        // the good news is that the config.json should have been cached already
         await initServiceWorker()
         // if event.resultingClientId is available, we need to use this
         // otherwise event.clientId is what we want
@@ -833,7 +840,17 @@ self.addEventListener('fetch', async event => {
  * assumptions to be considered:
  * every message contains clientId (so that we know where to respond if/when we need to)
  */
-self.addEventListener('message', (event) => {
+self.addEventListener('message', async (event) => {
+    
+    // initialize the SW; this is necessary as SW can be stopped at any time
+    // and restarted when an event gets triggered -- `message` is just such an event.
+    // 
+    // `install` and `activate` events only handle the initial installation of the SW
+    // this means that we might end up here without initServiceWorker() ever being run
+    // and so in a situation where plugins have never been actually set-up!
+    // 
+    // the good news is that the config.json should have been cached already
+    await initServiceWorker()
     
     // inform
     var msg = 'Message received!'