Added yarn translate:portal command

refs TryGhost#15502

- the amazing `i18next-parser` dependency will extract our translated
  strings from Portal and dump them into locale files, so we never have
  to add them manually

ghost/i18n/i18next-parser.config.js

@@ -0,0 +1,12 @@
+const {SUPPORTED_LOCALES} = require('./');
+
+module.exports = {
+    locales: SUPPORTED_LOCALES,
+
+    keySeparator: false,
+    namespaceSeparator: false,
+
+    sort: true,
+
+    output: 'locales/$LOCALE.json'
+};

ghost/i18n/lib/i18n.js

@@ -1,5 +1,16 @@
 const i18next = require('i18next');
 
+const RESOURCES = {
+    en: {
+        translation: require('../locales/en.json')
+    },
+    nl: {
+        translation: require('../locales/nl.json')
+    }
+};
+
+const SUPPORTED_LOCALES = Object.keys(RESOURCES);
+
 module.exports = (lng = 'en') => {
     const i18nextInstance = i18next.createInstance();
     i18nextInstance.init({
@@ -13,15 +24,10 @@ module.exports = (lng = 'en') => {
         // do not load a fallback
         fallbackLng: false,
 
-        resources: {
-            en: {
-                translation: require('../locales/en.json')
-            },
-            nl: {
-                translation: require('../locales/nl.json')
-            }
-        }
+        resources: RESOURCES
     });
 
     return i18nextInstance;
 };
+
+module.exports.SUPPORTED_LOCALES = SUPPORTED_LOCALES;

ghost/i18n/package.json

@@ -7,11 +7,12 @@
   "main": "index.js",
   "scripts": {
     "dev": "echo \"Implement me!\"",
-    "test:unit": "NODE_ENV=testing c8 --all --check-coverage --100  --reporter text --reporter cobertura mocha './test/**/*.test.js'",
+    "test:unit": "NODE_ENV=testing c8 --include index.js --include lib --check-coverage --100  --reporter text --reporter cobertura mocha './test/**/*.test.js'",
     "test": "yarn test:unit",
     "lint:code": "eslint *.js lib/ --ext .js --cache",
     "lint": "yarn lint:code && yarn lint:test",
-    "lint:test": "eslint -c test/.eslintrc.js test/ --ext .js --cache"
+    "lint:test": "eslint -c test/.eslintrc.js test/ --ext .js --cache",
+    "translate:portal": "i18next '../portal/src/**/*.{js,jsx}'"
   },
   "files": [
     "index.js",
@@ -20,6 +21,7 @@
   ],
   "devDependencies": {
     "c8": "7.12.0",
+    "i18next-parser": "7.6.0",
     "mocha": "10.2.0"
   },
   "dependencies": {