Examine source code of DeepLineBreaks

{
  "manifest_version": 2,
  "name": "DeepLineBreaks",
  "version": "1.7",
  "description": "Adds a button that allows to delete line breaks in the textarea of DeepL.",
  "icons": {
    "16": "icons/logo16.png",
    "48": "icons/logo48.png",
    "128": "icons/logo128.png",
    "256": "icons/logo256.png",
    "512": "icons/logo512.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.deepl.com/*"
      ],
      "js": [
        "deeplinebreaks.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ffa21afe-8fbc-478e-86c4-8d78e3ccf714}"
    }
  }
}