Toggle mjs files to javascript/auto type (facebook#5151)

Author: Timer

config/webpack.config.dev.js

@@ -187,6 +187,16 @@ module.exports = {
         ],
         include: paths.appSrc,
       },
+      {
+        // `mjs` support is still in its infancy in the ecosystem, so we don't
+        // support it.
+        // Modules who define their `browser` or `module` key as `mjs` force
+        // the use of this extension, so we need to tell webpack to fall back
+        // to auto mode (ES Module interop, allows ESM to import CommonJS).
+        test: /\.mjs$/,
+        include: /node_modules/,
+        type: 'javascript/auto',
+      },
       {
         // "oneOf" will traverse all following loaders until one will
         // match the requirements. When no loader matches it will fall

config/webpack.config.prod.js

@@ -244,6 +244,16 @@ module.exports = {
         ],
         include: paths.appSrc,
       },
+      {
+        // `mjs` support is still in its infancy in the ecosystem, so we don't
+        // support it.
+        // Modules who define their `browser` or `module` key as `mjs` force
+        // the use of this extension, so we need to tell webpack to fall back
+        // to auto mode (ES Module interop, allows ESM to import CommonJS).
+        test: /\.mjs$/,
+        include: /node_modules/,
+        type: 'javascript/auto',
+      },
       {
         // "oneOf" will traverse all following loaders until one will
         // match the requirements. When no loader matches it will fall