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.
buildGetDocumentParams(filename, {
          docBaseUrl: "http://www.example.com/test/pdfs/qwerty.pdf",
        })
      );
      const docBaseUrlPromise = docBaseUrlLoadingTask.promise.then(function (
        pdfDoc
      ) {
        return pdfDoc.getPage(1).then(function (pdfPage) {
          return pdfPage.getAnnotations();
        });
      });
      const invalidDocBaseUrlLoadingTask = getDocument(
        buildGetDocumentParams(filename, {
          docBaseUrl: "qwerty.pdf",
        })
      );
      const invalidDocBaseUrlPromise =
        invalidDocBaseUrlLoadingTask.promise.then(function (pdfDoc) {
          return pdfDoc.getPage(1).then(function (pdfPage) {
            return pdfPage.getAnnotations();
          });
        });
      const [
        defaultAnnotations,
        docBaseUrlAnnotations,
        invalidDocBaseUrlAnnotations,
      ] = await Promise.all([
        defaultPromise,
        docBaseUrlPromise,
        invalidDocBaseUrlPromise,