Translate all out-of-game UI (start screen, lobbies, etc.) (#316)

This PR adds full translation support for all out-of-game UI elements,
including the start screen, public/private lobby modals, and other
pre-game interfaces.

All static text has been externalized to en.json and ja.json for future
language support.
If you find any spots that are not yet translated (missing from the
JSON), please let me know.
Thanks a lot!

This is a follow-up to PR
[#305](https://github.com/openfrontio/OpenFrontIO/pull/305).

---------

Co-authored-by: Cldprv <dubois.cnm@tutanota.com>
Co-authored-by: jacks0n <rosty.west89@gmail.com>

src/client/Utils.ts

@@ -70,3 +70,30 @@ export function generateCryptoRandomUUID(): string {
     },
   );
 }
+
+export function translateText(
+  key: string,
+  params: Record<string, string | number> = {},
+): string {
+  const keys = key.split(".");
+  let text: any = (window as any).translations;
+
+  for (const k of keys) {
+    text = text?.[k];
+    if (!text) break;
+  }
+
+  if (!text && (window as any).defaultTranslations) {
+    text = (window as any).defaultTranslations;
+    for (const k of keys) {
+      text = text?.[k];
+      if (!text) return key;
+    }
+  }
+
+  for (const [param, value] of Object.entries(params)) {
+    text = text.replace(`{${param}}`, String(value));
+  }
+
+  return text;
+}