Update INSTALL.txt w/ htslib

INSTALL.txt

@@ -7,6 +7,7 @@ Dependencies:
    - GNU Scientific Library ( http://www.gnu.org/software/gsl/ )
    - CMake >=3.21
    - Zlib ( included with OS X and most Linuxes, http://www.zlib.net ) *
+   - [htslib](https://github.com/samtools/htslib)
 
 
 Steps:
@@ -19,5 +20,5 @@ Products:
    - command line tool ( build/bin/mashmap)
 
 
-* If Zlib and/or GSL is not installed in a standard system location (it usually is),
+* If Zlib, htslib, and/or GSL is not installed in a standard system location (it usually is),
   CXXFLAGS, LDFLAGS, and LD_LIBRARY_PATH will have to be modified before making and running.