Examine source code of remwhareadFF

{
    "manifest_version": 2,
    "name": "remwharead",
    "version": "0.5.0",

    "description": "Integrates remwharead into your Browser.",
    "homepage_url": "https://schlomp.space/tastytea/remwharead",

    "icons":
    {
        "16": "icon_dark.svg"
    },

    "applications":
    {
        "gecko":
        {
            "id": "remwharead@tastytea.de",
            "strict_min_version": "57.0"
        }
    },

    "permissions":
    [
        "activeTab",
        "nativeMessaging",
        "storage"
    ],

    "browser_action":
    {
        "default_title": "remwharead",
        "default_popup": "popup.html",
        "browser_style": true,
        "default_icon": "icon_dark.svg",
        "theme_icons":
        [{                      // Dark means dark text in Firefox. 🙄
            "dark": "icon_light.svg",
            "light": "icon_dark.svg",
            "size": 16
        }]
    },

    "options_ui":
    {
        "page": "options.html",
        "browser_style": true
    },

    "commands":
    {
        "_execute_browser_action":
        {
            "suggested_key":
            {
                "default": "Ctrl+Shift+S"
            },
            "description": "Open “Add URI”-popup."
        }
    }
}