Ensure code is compatible with node 12 (#543)

Author: mattcompiles

.changeset/odd-suits-call.md

@@ -0,0 +1,10 @@
+---
+'@vanilla-extract/babel-plugin': patch
+'@vanilla-extract/esbuild-plugin': patch
+'@vanilla-extract/integration': patch
+'@vanilla-extract/next-plugin': patch
+'@vanilla-extract/vite-plugin': patch
+'@vanilla-extract/webpack-plugin': patch
+---
+
+Ensure code is compatible with node 12

babel.config.js

@@ -1,5 +1,9 @@
 module.exports = {
-  presets: ['@babel/preset-typescript', '@babel/preset-react'],
+  presets: [
+    ['@babel/preset-env', { targets: { node: 12 } }],
+    '@babel/preset-typescript',
+    '@babel/preset-react',
+  ],
 
   overrides: [
     {