[doc/algorithms.tex] Add \pdfglyphtounicode{lscript}{2113} for \ell.

Otherwise one gets a grave accent (thus "s − l" cannot be found).
If the "ℓ" is still an issue, one could alternatively use
  \pdfglyphtounicode{lscript}{006C}
to get an "l" (but "l" also matches "ℓ" in xpdf and atril).

doc/algorithms.tex

@@ -37,6 +37,7 @@ Algorithms and Proofs}
 %   https://bugs.ghostscript.com/show_bug.cgi?id=704681
 %   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=995392
 \pdfglyphtounicode{prime}{2032}
+\pdfglyphtounicode{lscript}{2113}       % for \ell (or map to 006C)
 \pdfglyphtounicode{ceilingleft}{2308}
 \pdfglyphtounicode{ceilingright}{2309}
 \pdfglyphtounicode{floorleft}{230A}