Add instructions to propose different type of talks

Change-Id: I0341bde6a8bec160363074bcbad048a84bc52b73

cfp.md

diff --git a/cfp.md b/cfp.md
index f94d581..cd18988 100644
--- a/cfp.md
+++ b/cfp.md
@@ -13,6 +13,10 @@
 approach) and the entire Continuous Integration pipeline, including integration
 with specific CI systems (Jenkins or others) and with issue tracking systems.
 
+The talk can be submitted as a lightning talk (15 minutes) or a full length
+talk (40 minutes). For a lightning talk, follow the steps below, but use the
+`/lightning-talks` directory instead of `/sessions`.
+
 ## How to submit my proposal?
 
 It is very simple, just clone this project, create a Markdown document under