feat(i18n): add t() helper with locale detection and interpolation

src/i18n.ts

@@ -0,0 +1,26 @@
+// src/i18n.ts
+import { en } from "./lang/en";
+import { de } from "./lang/de";
+
+const locales: Record<string, Record<string, string>> = { en, de };
+
+/**
+ * Returns the translated string for `key` in the active Obsidian locale.
+ * Falls back to English if the locale or key is missing.
+ *
+ * Supports `{var}` interpolation:
+ *   t("noticePublishFailed", { error: "500" })
+ *   → "❌ Publish failed: 500"
+ */
+export function t(key: string, vars?: Record<string, string>): string {
+  const lang = (window.moment?.locale() ?? "en").split("-")[0];
+  const map  = locales[lang] ?? locales["en"];
+  let str    = map[key] ?? locales["en"][key] ?? key;
+
+  if (vars) {
+    for (const [k, v] of Object.entries(vars)) {
+      str = str.split(`{${k}}`).join(v); // replaceAll not available in ES2018
+    }
+  }
+  return str;
+}