[devhelp] readme: refer to the DhKeywordModel documentation for --search

[Sébastien Wilmet <swilmet src gnome org>]

commit 0b9a21ca18d41179cd5238b667d67773beda69b7
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sun Jan 21 12:29:32 2018 +0100

    readme: refer to the DhKeywordModel documentation for --search

 README |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/README b/README
index 6f20441..bc81d52 100644
--- a/README
+++ b/README
@@ -43,6 +43,10 @@ function_name under the cursor.
 Devhelp also provides a shared library, to integrate the GTK+ widgets inside an
 IDE. It is used for example by Builder and Anjuta.
 
+For the --search command line option, see the class description of
+DhKeywordModel, the search string supports additional features useful for IDEs
+or other developer tools.
+
 How it finds the API documentation
 ----------------------------------