Add react-i18next for multi-language support

cypress/e2e/i18n.cy.ts

@@ -0,0 +1,35 @@
+import { MaputnikDriver } from "./maputnik-driver";
+
+describe("i18n", () => {
+  let { beforeAndAfter, get, when, then } = new MaputnikDriver();
+  beforeAndAfter();
+
+  describe("language detector", () => {
+    it("English", () => {
+      const url = "?lng=en";
+      when.visit(url);
+      then(get.elementByTestId("maputnik-lang-select")).shouldHaveValue("en");
+    });
+
+    it("Japanese", () => {
+      const url = "?lng=ja";
+      when.visit(url);
+      then(get.elementByTestId("maputnik-lang-select")).shouldHaveValue("ja");
+    });
+  });
+
+  describe("language switcher", () => {
+    beforeEach(() => {
+      when.setStyle("layer");
+    });
+
+    it("the language switcher switches to Japanese", () => {
+      const selector = "maputnik-lang-select";
+      then(get.elementByTestId(selector)).shouldExist();
+      when.select(selector, "ja");
+      then(get.elementByTestId(selector)).shouldHaveValue("ja");
+
+      then(get.elementByTestId("nav:settings")).shouldHaveText("スタイル設定");
+    });
+  });
+});

cypress/e2e/maputnik-driver.ts

@@ -131,7 +131,9 @@ export class MaputnikDriver {
         this.helper.when.acceptConfirm();
       }
       // when methods should not include assertions
-      this.helper.get.elementByTestId("toolbar:link").should("be.visible");
+      const toolbarLink = this.helper.get.elementByTestId("toolbar:link")
+      toolbarLink.scrollIntoView();
+      toolbarLink.should("be.visible");
     },
 
     typeKeys: (keys: string) => this.helper.get.element("body").type(keys),

i18next-parser.config.ts

@@ -0,0 +1,17 @@
+export default {
+  output: 'src/locales/$LOCALE/$NAMESPACE.json',
+  locales: [ 'ja', 'he' ],
+
+  // Because some keys are dynamically generated, i18next-parser can't detect them.
+  // We add these keys manually, so we don't want to remove them.
+  keepRemoved: true,
+
+  // We use plain English keys, so we disable key and namespace separators.
+  keySeparator: false,
+  namespaceSeparator: false,
+
+  defaultValue: (locale, ns, key) => {
+    // The default value is a string that indicates that the string is not translated.
+    return '__STRING_NOT_TRANSLATED__';
+  }
+}