Update index.md

Add Platform Summit 2019 even if videos still unpublished for unknown reasons

Author: tlaurion

index.md

@@ -56,6 +56,7 @@ Conferences
 
 * [2016 - 33C3 - Trammel Hudson - Heads Presentation](https://trmm.net/Heads_33c3)
 * [2017 - 34C3 - Trammel Hudson - LinuxBoot Presentation](https://trmm.net/LinuxBoot_34c3/)
+* [2019 - Platform Security Summit - Thierry Laurion - Accessible Security: An OEM approach to transferring device and secrets ownership](https://www.platformsecuritysummit.com/2019/)
 * [2020 - FOSDEM - Thierry Laurion - Heads OEM device initial/trasfer of ownership](https://archive.fosdem.org/2020/schedule/event/firmware_hodorateatria/)
 * [2020 - SOCALINUXEXPO - Kyle Rankin - Tamper Evident Firmware with User-controlled keys](https://www.youtube.com/watch?v=NqQI3nr1dqk)
 * [2023 - FOSDEM - Thierry Laurion - Heads status update](https://archive.fosdem.org/2023/schedule/event/heads_status_update/)