Examine source code of PacePlay: Modern Speed control

{
  "name": "PacePlay : Modern Video Speed Controller",
  "short_name": "PacePlay",
  "version": "2.5",
  "manifest_version": 2,
  "description": "Speed up, slow down, advance and rewind HTML5 audio/video with shortcuts",
  "homepage_url": "https://github.com/moodynooby/paceplay-modern-speed-controller",
  "browser_specific_settings": {
    "gecko": {
      "id": "{7be2ba16-0f1e-4d93-9ebc-5464397477a9}"
    }
  },
  "icons": {
    "16": "icons/icon.svg",
    "48": "icons/icon.svg",
    "128": "icons/icon.svg"
  },
  "permissions": [
    "storage"
  ],
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "browser_action": {
    "default_icon": {
      "19": "icons/icon.svg",
      "38": "icons/icon.svg",
      "48": "icons/icon.svg"
    },
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "all_frames": true,
      "matches": [
        "http://*/*",
        "https://*/*",
        "file:///*"
      ],
      "match_about_blank": true,
      "exclude_matches": [
        "https://plus.google.com/hangouts/*",
        "https://www.google.com/flights/*",
        "https://hangouts.google.com/*",
        "https://meet.google.com/*"
      ],
      "css": [
        "inject.css"
      ],
      "js": [
        "inject.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "inject.css",
    "shadow.css"
  ]
}