make timeoutMs a read only property (set only in constructor)

src/loaders/TimedApiBasedRepositoryLoader.ts

@@ -10,7 +10,7 @@ export class TimedApiBasedRepositoryLoader {
 
   constructor(
     public loader: RepositoryLoader,
-    public timeoutMs: number = 10000,
+    public readonly timeoutMs: number = 10000,
   ) {
     this.startFetchDataAndUpdate = this.startFetchDataAndUpdate.bind(this);
   }