build: tweak Babel settings to match Scratch support FAQ

BREAKING CHANGE: this slightly changes our browser compatibility list

.babelrc

@@ -10,6 +10,8 @@
         [
             "@babel/preset-env",
             {
+                "bugfixes": true,
+
                 // This papers over the fact that our current code is inconsistent
                 // For example, we sometimes use `import` with a file that exports with `module.exports`
                 "modules": "commonjs"

package.json

@@ -177,8 +177,11 @@
     "all": true
   },
   "browserslist": [
-    "last 3 versions",
-    "Safari >= 8",
-    "iOS >= 8"
+    "Chrome >= 63",
+    "Firefox >= 57",
+    "Edge >= 15",
+    "Safari >= 11",
+    "ChromeAndroid >= 63",
+    "ios_saf >= 11"
   ]
 }

webpack.config.js

@@ -115,7 +115,7 @@ module.exports = {
     module: {
         rules: [
             {
-                test: /\.jsx?$/,
+                test: /\.(?:js|mjs|cjs)x?$/,
                 loader: 'babel-loader',
                 include: [
                     path.resolve(__dirname, 'src'),