added 'rr'

- signed-off-by: trimstray <trimstray@gmail.com>

README.md

@@ -217,6 +217,7 @@ Only main chapters:
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://en.wikipedia.org/wiki/Lsof"><b>lsof</b></a> - displays in its output information about files that are opened by processes.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="http://www.brendangregg.com/flamegraphs.html"><b>FlameGraph</b></a> - stack trace visualizer.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/zevv/lsofgraph"><b>lsofgraph</b></a> - small utility to convert Unix lsof output to a graph showing FIFO and UNIX interprocess communication.<br>
+&nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/mozilla/rr"><b>rr</b></a> - is a lightweight tool for recording, replaying and debugging execution of applications.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://pcp.io/index.html"><b>Performance Co-Pilot</b></a> - a system performance analysis toolkit.</br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/sharkdp/hexyl"><b>hexyl</b></a> - a command-line hex viewer.<br>
 </p>