Attach (recommended) or Link to PDF file here:
[output.pdf](https://github.com/mozilla/pdf.js/files/6374987/output.pdf)

Configuration:
- Web browser and its version: Firefox 88.0
- Operating system and its version: macOS Big Sur 11.2.3 (20D91)
- PDF.js version: 2.8.243
- Is a browser extension: no/Firefox built-in

Steps to reproduce the problem:
1.  add Ink-Annotations to a pdf (i use https://github.com/highkite/pdfAnnotate, Annotations with appearance streams are shown correctly)
2. open output file in firefox

What is the expected behavior? 
The annotations should be visible.
![Bildschirmfoto 2021-04-26 um 09 15 48](https://user-images.githubusercontent.com/33630884/116043809-6a020f80-a670-11eb-973c-6f2df3dae532.png)

What went wrong? 
The annotations are added to the dom but invisible.
![Bildschirmfoto 2021-04-26 um 09 18 26](https://user-images.githubusercontent.com/33630884/116043867-7e460c80-a670-11eb-964d-0cc2c6dbfb61.png)

Tested successfull with FoxitReader, AcrobatReader, Chrome and Safari.
}
    for (const resources of [localResources, appearanceResources]) {
      if (resources instanceof Dict) {
        const localFont = resources.get("Font");
        if (localFont instanceof Dict && localFont.has(fontName)) {
          return resources;
        }
      }
    }
    if (acroFormResources instanceof Dict) {
      const acroFormFont = acroFormResources.get("Font");
      if (acroFormFont instanceof Dict && acroFormFont.has(fontName)) {
        const subFontDict = new Dict(xref);
        subFontDict.set(fontName, acroFormFont.getRaw(fontName));
        const subResourcesDict = new Dict(xref);
        subResourcesDict.set("Font", subFontDict);
        return Dict.merge({
          xref,
          dictArray: [subResourcesDict, localResources],
          mergeSubDicts: true,
        });
      }
    }
    return localResources || Dict.empty;
  }
  getFieldObject() {
    return null;
  }
}
class TextWidgetAnnotation extends WidgetAnnotation {