I don't recommend this option, because it is hard to maintain, but sometimes you just have a small project that you don't want to spend any unnecessary time on, and using the stand-alone .js files is fine for you.
Instead of having to download the files yourself, you can directly link to the unpkg host like this:
Dropzone is now active and available as window.Dropzone.
Note that the imported css file is optional.
Dropzone has dropped Internet Explorer support in version 6, which is still in beta this point. If you already want to use a much lighter script (46kB vs 115kB) and don't care about Internet Explorer support, you can already opt into it like this: