Fix blocking I/O

[riobits]

The writeFile function helps prevent blocking I/O. Please test the code because I didn't test it.

[riobits]

Error handling should be managed inside a try/catch block. Documentation needs an update.

1. Error handling

   try {
   await storeFileLocally(
   file.content, 
   file.name, 
   '/userFiles'
   )
   } catch(err) {
   // ...
   }

2. Explain the deleteFile function