Update README.md

[nerg4l]

On reddit a user mentioned that the README is not clear. Link for the comment

Kudos for reaching out to the community and actually asking for help.

Unfortunately, my own projects currently suck up all my free time, so I can't join you. :(

However, I still want to give a little feedback:

The README or the description of https://github.com/LaraCrafts/laravel-chunk-uploader is quite vage. "Laravel Chunk Uploader - Chunk Uploader Package For Laravel" doesn't tell me much. 😅

I have an idea of what the package does, but just looking at the README, I can't confirm that. My guess is, that it helps me add something like dropzone.js to my project, and the package will somehow handle the upload for me? What does handle really mean?

I've never worked with chunk uploads before. So maybe it's just my naivety. 😅

This PR tries to clarify what the library does and tell the ambiguity behind the word "handle".