fix(react-email): NODE_ENV for emails as "PRODUCTION"

Author: gabrielmfern

.changeset/gorgeous-ravens-tease.md

@@ -0,0 +1,5 @@
+---
+"react-email": patch
+---
+
+Fix NODE_ENV for emails as "PRODUCTION" instead of "DEVELOPMENT"

packages/react-email/src/cli/utils/preview/start-dev-server.ts

@@ -120,6 +120,7 @@ export const startDevServer = async (
   // this is the most reliable way of communicating these paths through
   process.env = {
     ...process.env,
+    NODE_ENV: "development",
     ...getEnvVariablesForPreviewApp(
       // If we don't do normalization here, stuff like https://github.com/resend/react-email/issues/1354 happens.
       path.normalize(emailsDirRelativePath),