Add additional documentation for workerPath config (#5765)

MIGRATING.md

@@ -1,3 +1,11 @@
+# Migrating from hls.js 1.x to 1.4+
+
+The 1.4 version of hls.js now ships with an ESM version of the library (`dist/hls.mjs`) which requires that you specify the [`workerPath` config option](https://github.com/video-dev/hls.js/blob/master/docs/API.md#workerpath) in order for web workers to be used. This should point to the `dist/hls.worker.js` file included in the package.
+
+If you are using the UMD version (`dist/hls.js`), no changes are required.
+
+**Important Note:** If you are using a bundler, such as webpack, the ESM version of the package will likely be used by default. If this is the case, make sure to add the `workerPath` config option after upgrading to hls.js 1.4 or above.
+
 # Migrating from hls.js 0.x to 1.x
 
 This guide provides an overview to migrating an application using hls.js from v0.14.x to v1.0.0.

docs/API.md

@@ -207,7 +207,13 @@ Let's
 <script>
   if (Hls.isSupported()) {
     var video = document.getElementById('video');
+
+    // If you are using the ESM version of the library (hls.mjs), you
+    // should specify the "workerPath" config option here if you want
+    // web workers to be used. Note that bundlers (such as webpack)
+    // will likely use the ESM version by default.
     var hls = new Hls();
+
     // bind them together
     hls.attachMedia(video);
     // MEDIA_ATTACHED event is fired by hls object once MediaSource is ready
@@ -669,6 +675,8 @@ Enable WebWorker (if available on browser) for TS demuxing/MP4 remuxing, to impr
 
 Provide a path to hls.worker.js as an alternative to injecting the worker based on the iife library wrapper function. When `workerPath` is defined as a string, the transmuxer interface will initialize a WebWorker using the resolved `workerPath` URL.
 
+When using the ESM version of the library (hls.mjs), this option is required in order for web workers to be used.
+
 ### `enableSoftwareAES`
 
 (default: `true`)