Add PSR-3 log implementation to phan configuration
Summary:
This fixes the following issue detected by phan:
app/Exceptions/Handler.php:49 PhanUndeclaredClassMethod Call to method error from undeclared class \Psr\Log\LoggerInterface
Test Plan: phan | grep Psr
Reviewers: dereckson
Reviewed By: dereckson
Differential Revision: https://devcentral.nasqueron.org/D779