Attach (recommended) or Link to PDF file here:
[example.pdf](https://github.com/mozilla/pdf.js/files/6916129/example.pdf)

Configuration:
- Web browser and its version: Chrome, Firefox
- Operating system and its version: all
- PDF.js version: various versions, including 2.11.54
- Is a browser extension: no

Screenshot with visible textLayer:
![Screenshot from 2021-08-02 13-05-03](https://user-images.githubusercontent.com/6362989/127844878-f85e291f-2060-4028-be09-7835f32ccfaa.png)

Which means some letters at the beginning/end of text selection are missing when copying text.

numGlyphs,
      dupFirstEntry
    ) {
      if (!header) {
        if (metrics) {
          metrics.data = null;
        }
        return;
      }
      file.pos = (file.start ? file.start : 0) + header.offset;
      file.pos += 4; 
      file.pos += 2; 
      file.pos += 2; 
      file.pos += 2; 
      file.pos += 2; 
      file.pos += 2; 
      file.pos += 2; 
      file.pos += 2; 
      file.pos += 2; 
      file.pos += 2; 
      const caretOffset = file.getUint16();
      file.pos += 8; 
      file.pos += 2; 
      let numOfMetrics = file.getUint16();
      if (caretOffset !== 0) {
        const macStyle = int16(headTable.data[44], headTable.data[45]);
        if (!(macStyle & 2)) {
          
          header.data[22] = 0;
          header.data[23] = 0;