feat: add translation support (#2870)

* feat: add translation support

* test(cypress): fix locale import

* docs: add locale documentation

* feat: add german translation (#2877)

* fix: locales package version, register all locales in netlify-cms

packages/netlify-cms-locales/package.json

@@ -0,0 +1,21 @@
+{
+  "name": "netlify-cms-locales",
+  "description": "Locales for Netlify CMS.",
+  "version": "1.0.0",
+  "repository": "https://github.com/netlify/netlify-cms/tree/master/packages/netlify-cms-locales",
+  "bugs": "https://github.com/netlify/netlify-cms/issues",
+  "license": "MIT",
+  "module": "dist/esm/index.js",
+  "main": "dist/netlify-cms-locales.js",
+  "keywords": [
+    "netlify-cms"
+  ],
+  "sideEffects": false,
+  "scripts": {
+    "develop": "yarn build:esm --watch",
+    "build": "cross-env NODE_ENV=production webpack",
+    "build:esm": "cross-env NODE_ENV=esm babel src --out-dir dist/esm --ignore \"**/__tests__\" --root-mode upward"
+  },
+  "dependencies": {},
+  "peerDependencies": {}
+}