Feature Request: support reading config from browser policies

For example, uBlock supports being configured via browser policies - this pairs very nicely with NixOS and/or Home Manager where such policy files can be managed declaratively (and stored on disk, potentially version controlled, maintained uniformly between different computers, ...).

With support for reading the config from a browser policy, configuring Vimium via Home Manager would look something like:

programs.firefox = {
  enable = true;
  policies = {
    ExtensionSettings = {
      # Install the extension
      "{d7742d87-e61d-4b78-b8a1-b469842139fa}" = {
        install_url = "https://addons.mozilla.org/firefox/downloads/latest/vimium-ff/latest.xpi";
        installation_mode = "force_installed";
        default_area = "navbar";
      }; 
    };
    "3rdparty".Extensions = {
      # Configure the extension - reading these values from the browser's policy store is the feature request
      "{d7742d87-e61d-4b78-b8a1-b469842139fa}" = {
        scrollStepSize = 50;
        keyMappings = ''
          unmapAll
          map <a-j> scrollPageDown
          ...
        '';
      };
    };
  };
};

This would be a really nice workflow for managing Vimium settings.

Read the linked uBlock browser-policy example and the NixOS/Home Manager context first. Then identify Vimium’s existing settings-loading path and how the browser exposes extension policies. Done means supported policy values are read as Vimium settings without breaking existing configuration sources, with coverage for the requested workflow.