fix: Avoid auto-reload for recently created source directory

Watchpack has a bug that caused it to dispatch change events for files
that were created recently (up to 2 seconds before now). This can
trigger an unwanted auto-reload, e.g. in the scenario of an extension
developer building an extension and using `web-ext run` to immediately
launch that built package.

Author: Rob--W

src/watcher.js

@@ -63,7 +63,9 @@ export default function onSourceChange({
     files: watchedFiles,
     directories: watchedDirs,
     missing: [],
-    startTime: Date.now(),
+    // startTime: Date.now(), is explicitly NOT set because it causes onChange
+    // to be emitted if the files were created shortly before now!
+    // See https://github.com/webpack/watchpack/issues/295
   });
 
   // TODO: support interrupting the watcher on Windows.