New test suggestion - Leaf node certificate used as intermediate

[DavisNT]

A simple certificate issue not yet covered by badssl.com tests is a leaf node certificate (with CA:FALSE in Basic Constraints field) used as intermediate certificate somewhere in the chain.
I think a good test would be something like leaf-node.badssl.com which would use a certificate signed by the valid leaf node certificate of badssl.com.
A very similar issue would be having a leaf node higher in the certificate chain. Maybe these two cases could be combined and the certificate of leaf-node.badssl.com could be signed by 2 certificates (both sent by the server and maybe also available via the AIA CA Issuers links):

1. the valid leaf node certificate of badssl.com (i.e. directly by the leaf node);
2. a self-generated intermediate certificate (with CA:TRUE in Basic Constraints field) signed by the valid leaf node certificate of badssl.com (i.e. having the leaf node higher in the chain).

It could also be valuable to include this test in the dashboard.