Platform: Add support for BL5340 DVK

This adds supports for the Laird Connectivity BL5340 DVK (development kit)
application core, which is based on the nRF5340 SoC.

Signed-off-by: Jamie McCrae <jamie.mccrae@lairdconnect.com>
Change-Id: I062412918d4cbe692748c1a31fef444190f50661
diff --git a/platform/ext/index.rst b/platform/ext/index.rst
index 1d12b9a..edd2cf6 100644
--- a/platform/ext/index.rst
+++ b/platform/ext/index.rst
@@ -48,6 +48,13 @@
 
 .. toctree::
     :maxdepth: 4
+    :caption: Laird Connectivity
+    :glob:
+
+    target/lairdconnectivity/**
+
+.. toctree::
+    :maxdepth: 4
     :caption: Nuvoton
     :glob: