Add Fortify scanner THREAT_MODEL.md to dot-net-framework-url-escaping repo Bug: b/548453908 Change-Id: I95af7b986241d794c09404030d5fd639ae2ce259 Reviewed-on: https://gnocchi-internal-review.git.corp.google.com/c/third_party/dot-net-framework-uri-escaping/+/314964 Reviewed-by: Trevor Ryland <tryland@google.com>