Update metro config to support loading .cjs files

Workaround for metro deficiency: facebook/metro#535

Caused by stylis shipping a .cjs file: thysultan/stylis#233

Fix from emotion-js/emotion#1986

metro.config.js

@@ -1,17 +1,21 @@
-/**
- * Metro configuration for React Native
- * https://github.com/facebook/react-native
- *
- * @format
- */
+const { getDefaultConfig } = require('metro-config');
 
-module.exports = {
-    transformer: {
-        getTransformOptions: async () => ({
-            transform: {
-                experimentalImportSupport: false,
-                inlineRequires: false,
-            },
-        }),
-    },
-};
+module.exports = (async () => {
+    const {
+        resolver: { sourceExts },
+    } = await getDefaultConfig();
+    return {
+        resolver: {
+            // Add cjs extension so stylis will load.
+            sourceExts: [...sourceExts, 'cjs'],
+        },
+        transformer: {
+            getTransformOptions: async () => ({
+                transform: {
+                    experimentalImportSupport: false,
+                    inlineRequires: false,
+                },
+            }),
+        },
+    };
+})();