Before you start implementing new features, please create an issue about it first and discuss your intent.
It might be something that someone else is already implementing or that goes against the concepts of Dropzone, and I really hate rejecting pull requests others spent hours writing on.
The first thing you need to do, is to install the developer dependencies:
$ yarn installThis will install all the tools you need to compile the source files and to test the library.
Testing is done on the compiled files. So either run yarn build or
yarn watch first, and then yarn test.
In order to run the cypress tests (e2e tests), you need to first start the
test server (yarn start-test-server) and then cypress yarn cypress open.