Make unhandled promise errors in build and tests fatal

It is expected that this will cause CI to fail, since there are unfixed errors.

Fixes #4

bin/build-schemas.ts

@@ -95,4 +95,9 @@ async function* walk(
   }
 }
 
+process.on("unhandledRejection", (reason, promise) => {
+  console.log("Unhandled Reject at:", promise, "reason:", reason);
+  process.exit(1);
+});
+
 main();

test/normandy-arguments.ts

@@ -48,4 +48,9 @@ function convertActionNameToTypeName(actionName: string): string {
   return typeName + "Arguments";
 }
 
+process.on("unhandledRejection", (reason, promise) => {
+  console.log("Unhandled promise rejection:", reason);
+  process.exit(1);
+});
+
 main();