feat: add core i18n runtime and catalogs

lib/i18n/translator.ts

@@ -0,0 +1,22 @@
+import { interpolateMessage } from "./format";
+import type { TranslationValues } from "./types";
+
+export type Translator = {
+  locale: string;
+  messages: Record<string, string>;
+  t: (key: string, values?: TranslationValues) => string;
+};
+
+export function createTranslatorFromMessages(
+  locale: string,
+  messages: Record<string, string>,
+): Translator {
+  return {
+    locale,
+    messages,
+    t(key, values) {
+      const message = messages[key] ?? key;
+      return interpolateMessage(message, values, locale);
+    },
+  };
+}