samples: thrift: update doc to include optional modules

Update the Thrift sample to include instructions on
fetching optional modules. Without this, user builds
will fail.

Signed-off-by: Christopher Friedt <[email protected]>

Author: Christopher Friedt

samples/modules/thrift/hello/README.rst

@@ -48,6 +48,14 @@ layers in thrift can be combined to build an application with desired features.
 Requirements
 ************
 
+- Optional Modules
+
+.. code-block:: console
+   :caption: Download optional modules with west
+
+   west config manifest.group-filter -- +optional
+   west update
+
 - QEMU Networking (described in :ref:`networking_with_qemu`)
 - Thrift dependencies installed for your host OS e.g. in Ubuntu