Made it so you can configure everything

You can configure the following settings:
- Placeholder artwork URL
- Paused timeout (in seconds, minutes, or hours)
- Metadata fetch interval (in seconds, minutes, or hours)

I also added helping notes to the title of the inputs to make it clearer what each setting does.

Also meow meow meow meow meow meow meow meow meow meow meow meow meow meow

manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "Apple Music Now Playing",
-  "version": "1.4.2",
+  "version": "1.4.3",
   "description": "Easily display your currently playing Apple Music track on your website with this extension.",
   "permissions": [
     "storage",