[pitivi] help: copy section from crossfading.page to transitions.page and update it

[Jean-François Fortin Tam <jfft src gnome org>]

commit 265896cf633836ffb29300577e9d7428b5322dc6
Author: Tomas Karger <tomkarger gmail com>
Date:   Fri Mar 28 13:41:29 2014 +0100

    help: copy section from crossfading.page to transitions.page and update it

 help/C/transitions.page |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/help/C/transitions.page b/help/C/transitions.page
index 2fa7ea1..117a86f 100644
--- a/help/C/transitions.page
+++ b/help/C/transitions.page
@@ -26,5 +26,12 @@
 
     <title>Transitions</title>
 
+    <section>
+      <title>Crossfading clips</title>
+        <p>To do a crossfade between two clips on the same layer, simply drag one of the clips onto the 
other so that it overlaps. The overlapping region will be used as a space for transition between the two 
clips. You can adjust the length of the transition either by moving the clips or by trimming them. If you 
want to apply other types of transitions than the default (crossfade), see the <em>Other types of 
transitions</em> section on this page.</p>
+      <note>
+        <p>Crossfades are achieved using <app>Pitivi</app>'s video mixing features, which use keyframes to 
control the opacity of clips. This means that if you set opacity keyframes for a clip, they will be taken 
into account for the crossfade.</p>
+      </note>
+    </section>
 
 </page>