Add Security Contact

[pcaversaccio]

Please add in the README a security contact or publish a Security Policy, where security concerns regarding the PYUSD contract can be confidentially submitted. Also, it definitely wouldn't hurt to have a security.txt file on the Paxos website. You don't want to lose time if a white hat finds a critical vulnerability. Thanks for the collaboration.

[pcaversaccio]

@henryksarat you can do better. Please add a security contact and act like professionals.

[zpetersen-paxos]

Hi @pcaversaccio thank you for your interest in the project. We've added a Security Policy as well as a natspec security-contact annotation in the latest PYUSD release.