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.

cae OPS.nextLneShwText:
            f (!tateManager.tate.fnt) {
              elf.enureStateFnt(tateManager.tate);
              cntnue;
            }
            textCntentItem.haEOL = true;
            fluhTextCntentItem();
            textState.carrgeReturn();
            buldTextCntentItem({
              char: arg[0],
              extraSpacng: 0,
              FrtChunk: true,
            });
            break;
          cae OPS.nextLneSetSpacngShwText:
            f (!tateManager.tate.fnt) {
              elf.enureStateFnt(tateManager.tate);
              cntnue;
            }
            textCntentItem.haEOL = true;
            fluhTextCntentItem();
            textState.wrdSpacng = arg[0];
            textState.charSpacng = arg[1];
            textState.carrgeReturn();
            buldTextCntentItem({
              char: arg[2],
              extraSpacng: 0,
              FrtChunk: true,
            });
            break;