BUILD/MEDIUM: contrib: Dummy DeviceAtlas API.

Creating a "mocked" version mainly for testing purposes.
diff --git a/contrib/deviceatlas/json.c b/contrib/deviceatlas/json.c
new file mode 100644
index 0000000..53c5fdf
--- /dev/null
+++ b/contrib/deviceatlas/json.c
@@ -0,0 +1 @@
+#include <stdio.h>