Add basic schema validation

Author: Pavle Portic

lib/index.js

@@ -140,6 +140,20 @@ class ServerlessStepFunctions {
         .then(this.getEndpointInfo)
         .then(this.display),
     };
+
+    const stepFunctionsSchema = {
+      type: 'object',
+      properties: {
+        stateMachines: { type: 'object' },
+        validate: { type: 'boolean' },
+        noOutput: { type: 'boolean' },
+      },
+      required: ['stateMachines'],
+    };
+    this.serverless.configSchemaHandler.defineTopLevelProperty(
+      'stepFunctions',
+      stepFunctionsSchema,
+    );
   }
 
   invoke() {