Update communitybeats.asciidoc (elastic#3606)

Add link to iobeat which reads and publishes IO statistics from /proc/diskstats on Linux.

libbeat/docs/communitybeats.asciidoc

@@ -27,6 +27,7 @@ https://github.com/YaSuenag/hsbeat[hsbeat]:: Reads all performance counters in J
 https://github.com/christiangalsterer/httpbeat[httpbeat]:: Polls multiple HTTP(S) endpoints and sends the data to
 Logstash or Elasticsearch. Supports all HTTP methods and proxies.
 https://github.com/jasperla/hwsensorsbeat[hwsensorsbeat]:: Reads sensors information from OpenBSD.
+https://github.com/devopsmakers/iobeat[iobeat]:: Reads IO stats from /proc/diskstats on Linux.
 https://github.com/radoondas/jmxproxybeat[jmxproxybeat]:: Reads Tomcat JMX metrics exposed over 'JMX Proxy Servlet' to HTTP.
 https://github.com/mheese/journalbeat[journalbeat]:: Used for log shipping from systemd/journald based Linux systems.
 https://github.com/eskibars/lmsensorsbeat[lmsensorsbeat]:: Collects data from lm-sensors (such as CPU temperatures, fan speeds, and voltages from i2c and smbus).