index.rst: include LVGL documentation

Relate-to: eclipse/oniro-core/oniro!331 (comment 1025298)


Signed-off-by: Philippe Coval <philippe.coval.ext@huawei.com>

index.rst

@@ -73,6 +73,7 @@ daily life.
    oniro/supported-technologies/openthread
    oniro/supported-technologies/containers
    oniro/supported-technologies/modbus
+   oniro/supported-technologies/lvgl
 
 .. toctree::
    :caption: Supported Toolchains