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### Preflight Checklist
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* [x] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
* [x] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
* [x] I have searched the issue tracker for a feature request that matches the one I want to file, without success.

### Problem Description
<!-- Is your feature request related to a problem? Please add a clear and concise description of what the problem is. -->

They is no way to choose the paper format (A4, A3, Letter, ...) when printing with `webContents.print()`.

### Proposed Solution
<!-- Describe the solution you'd like in a clear and concise manner -->

Add something like the `pageSize` option which is available in [`webContents.printToPDF()`](https://electronjs.org/docs/api/web-contents#contentsprinttopdfoptions-callback).

shell/browser/api/electron_api_web_contents.cc
v8::Local<v8::Value> val,
                     printing::DuplexMode* out) {
    std::string mode;
    if (ConvertFromV8(isolate, val, &mode)) {
      if (mode == "simplex") {
        *out = printing::SIMPLEX;
        return true;
      }
      if (mode == "longEdge") {
        *out = printing::LONG_EDGE;
        return true;
      }
      if (mode == "shortEdge") {
        *out = printing::SHORT_EDGE;
        return true;
      }
    }
    return false;
  }
};
#endif
template <>
struct Converter<WindowOpenDisposition> {
  static v8::Local<v8::Value> ToV8(v8::Isolate* isolate,