Add link to Explain SAM flags

presentation.tex

@@ -377,6 +377,11 @@
     r002  99  ref  7  30  8M2I4M1D3M = 37  39 TTAGATAAAGGATACTG *
     r002 147  ref 37  30  9M         =  7 -39 CAGCGGCAT         * NM:i:1
   \end{Verbatim}
+
+  \bigskip
+  \pause
+  \vspace{1em}
+  \scriptsize Explain SAM flags \url{https://broadinstitute.github.io/picard/explain-flags.html}
 \end{pframe}