Add .bundle string inclusion check (#14)

* Add .bundle string suffix check

Sources/LocalizedStringKit/LocalizedStringKit.m

@@ -115,7 +115,7 @@ NSBundle *getLocalizedStringKitBundle(NSString *_Nullable bundleName) {
     // Defaults to primary bundle if bundleName not specified
     bundleName = LSKPrimaryBundleName;
   }
-  else
+  else if (![bundleName hasSuffix:@".bundle"])
   {
     // Append suffix
     bundleName = [bundleName stringByAppendingFormat:@".bundle"];