feat: translator can set the cache time uniformly via the constructor

src/index.ts

@@ -9,8 +9,10 @@ const cache = new Cache();
 
 class Translator {
   private engines: Map<string, Engine>;
-  constructor() {
+  private cache_time: number;
+  constructor(cache_time: number = 60 * 1000) {
     this.engines = new Map<string, Engine>();
+    this.cache_time = cache_time;
   }
   use(engine: Engine) {
     if (this.engines.has(engine.name)) {
@@ -49,7 +51,7 @@ class Translator {
     }
 
     return engineInstance.translate(text, options).then((translated) => {
-      cache.set(key, translated, cache_time);
+      cache.set(key, translated, cache_time ?? this.cache_time);
       return translated;
     });
   }
@@ -60,6 +62,7 @@ const translator = new Translator();
 export default {
   engines,
   translator,
+  Translator,
   Cache,
   getLanguage,
 };