Attach (recommended) or Link to PDF file here:
https://bitcoin.org/bitcoin.pdf

Configuration:
- Web browser and its version: all
- Operating system and its version: all
- PDF.js version: tested with 2.9.11, but most likely all versions
- Is a browser extension: no

Steps to reproduce the problem:
1. Type "a purely" (single space between "a" and "purely") - doesn't find anything
2. Type "a  purely" (two spaces between "a" and "purely") - finds the phrase

Sometimes even 3 spaces are necessary.

What is the expected behavior? (add screenshot)
![Screenshot from 2021-04-08 13-00-03](https://user-images.githubusercontent.com/6362989/114008903-57639a00-986b-11eb-903a-92bbebbd922b.png)

What went wrong? (add screenshot)
![Screenshot from 2021-04-08 13-01-53](https://user-images.githubusercontent.com/6362989/114008810-44e96080-986b-11eb-8232-f58a62ed7899.png)

This affects many PDFs because justify alignment is common enough.
const numPages = pdfDoc.numPages;
      expect(numPages).toEqual(3);
      const viewPromises = [];
      for (let i = 0; i < numPages; i++) {
        viewPromises[i] = pdfDoc.getPage(i + 1).then(pdfPage => {
          return pdfPage.view;
        });
      }
      const [page1, page2, page3] = await Promise.all(viewPromises);
      expect(page1).toEqual([0, 0, 612, 792]);
      expect(page2).toEqual([0, 0, 800, 600]);
      expect(page3).toEqual([0, 0, 600, 800]);
      await viewLoadingTask.destroy();
    });
    it("gets viewport", function () {
      const viewport = page.getViewport({ scale: 1.5, rotation: 90 });
      expect(viewport.viewBox).toEqual(page.view);
      expect(viewport.scale).toEqual(1.5);
      expect(viewport.rotation).toEqual(90);
      expect(viewport.transform).toEqual([0, 1.5, 1.5, 0, 0, 0]);
      expect(viewport.width).toEqual(1262.835);
      expect(viewport.height).toEqual(892.92);
    });
    it('gets viewport with "offsetX/offsetY" arguments', function () {
      const viewport = page.getViewport({
        scale: 1,
        rotation: 0,
        offsetX: 100,
        offsetY: -100,
      });