chore(release): publish

- netlify-cms-app@2.15.4
 - netlify-cms-core@2.40.1
 - netlify-cms-proxy-server@1.3.14
 - netlify-cms@2.10.124

packages/netlify-cms-app/package.json

@@ -1,7 +1,7 @@
 {
   "name": "netlify-cms-app",
   "description": "An extensible, open source, Git-based, React CMS for static sites. Reusable congiuration with React as peer.",
-  "version": "2.15.3",
+  "version": "2.15.4",
   "homepage": "https://www.netlifycms.org",
   "repository": "https://github.com/netlify/netlify-cms/tree/master/packages/netlify-cms-app",
   "bugs": "https://github.com/netlify/netlify-cms/issues",
@@ -40,7 +40,7 @@
     "netlify-cms-backend-gitlab": "^2.11.1",
     "netlify-cms-backend-proxy": "^1.2.0",
     "netlify-cms-backend-test": "^2.11.0",
-    "netlify-cms-core": "^2.40.0",
+    "netlify-cms-core": "^2.40.1",
     "netlify-cms-editor-component-image": "^2.7.0",
     "netlify-cms-lib-auth": "^2.4.0",
     "netlify-cms-lib-util": "^2.13.0",