fix: add a cjs export

Author: fgnass

packages/decap-cms-app/package.json

@@ -19,7 +19,8 @@
       "require": "./dist/decap-cms-app.js"
     },
     "./init": {
-      "import": "./dist/esm/init/index.js"
+      "import": "./dist/esm/init/index.js",
+      "require": "./src/init/esm-only.cjs"
     }
   },
   "scripts": {

packages/decap-cms-app/src/init/esm-only.cjs

@@ -0,0 +1,15 @@
+function error() {
+  throw new Error(
+    'The "decap-cms-app/init" subpath is only available in ESM environments.\n' +
+      'Please make sure you are using it in an ESM context (e.g. with "type": "module" in your package.json).',
+  );
+}
+
+exports.registerBackend = error;
+exports.registerCoreWidgets = error;
+exports.registerMapWidget = error;
+exports.registerCodeWidget = error;
+exports.registerImageComponent = error;
+exports.registerLocale = error;
+exports.registerAll = error;
+exports.init = error;