Revert "Revert "Add Snyk policy file (#1033)" (#1034)"

This reverts commit 88f23cd.

Author: bigmontz

.snyk

@@ -0,0 +1,9 @@
+# Snyk (https://snyk.io) policy file
+exclude:
+ global:
+  - packages/testkit-backend/**
+  - testkit/**
+  - packages/core/test/**
+  - packages/bolt-connection/test/**
+  - packages/neo4j-driver-lite/test/**
+  - packages/neo4j-driver/test/**