[geary] Add documentation for new is:foo search operators. Bug 726661.

[Adam Dingle <adamd src gnome org>]

commit 77b1c26b540006df710bff109c13e6f4074e22ed
Author: Michael James Gratton <mike vee net>
Date:   Fri Apr 29 23:52:39 2016 +1000

    Add documentation for new is:foo search operators. Bug 726661.

 help/C/search.page |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)
---
diff --git a/help/C/search.page b/help/C/search.page
index 57471db..218116e 100644
--- a/help/C/search.page
+++ b/help/C/search.page
@@ -44,6 +44,18 @@
                <td><p>Finds messages where <var>sender</var> matches the From header.</p></td>
        </tr>
        <tr>
+               <td><p><input>is:read</input></p></td>
+               <td><p>Finds messages that have been marked as read.</p></td>
+       </tr>
+       <tr>
+               <td><p><input>is:starred</input></p></td>
+               <td><p>Finds messages that have been marked as starred.</p></td>
+       </tr>
+       <tr>
+               <td><p><input>is:unread</input></p></td>
+               <td><p>Finds messages that have been marked as not read.</p></td>
+       </tr>
+       <tr>
                <td><p><input>subject:<var>text</var></input></p></td>
                <td><p>Finds messages whose subject contains <var>text</var>.</p></td>
        </tr>