[evolution] Add a link to an online build manual into the README

[Milan Crha <mcrha src gnome org>]

commit 805ef64d46309f11e4b328faa0e841c0b7b561cf
Author: Milan Crha <mcrha redhat com>
Date:   Wed Apr 3 18:25:42 2019 +0200

    Add a link to an online build manual into the README

 README | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/README b/README
index 9be805c7ca..a15baf26ce 100644
--- a/README
+++ b/README
@@ -147,3 +147,9 @@ After the Evolution is properly configured, run:
                 make -j install
 
 to build it.
+
+ONLINE BUILD MANUAL
+-------------------
+
+An online build manual can be found here:
+https://wiki.gnome.org/Apps/Evolution/Building