Manifest v3 migration

[ave1217]

I have been using this extension for a while but it seems like an update is needed due to the manifest version change from v2 to v3.

[jcobb48]

@ave1217 @dannyfan I tested replacing manifest.json content with this and it works:

{
    "name" : "Crunchyroll Playback Speed Controller",
    "version" : "1.2.0",
    "description" : "Extension to change Crunchyroll's video playback speed.",
    "background": {
        "service_worker": "background.js",
        "type": "module"
    },
    "action": {
        "default_popup": "popup.html"
    },
    "content_scripts": [
        {
          "matches": ["https://*.crunchyroll.com/*"],
          "run_at": "document_end",
          "all_frames": true,
          "js": ["playback.js"]
        }
      ],
    "permissions": ["activeTab", "declarativeContent", "storage"],
    "manifest_version" : 3
}