fix #3700 DropZone document

[malanjp]

WHY are these changes introduced?

Fixes #3700

WHAT is this pull request doing?

Change from validImageTypes.indexOf(file.type) > 0 to validImageTypes.indexOf(file.type) > -1.

[ghost]

👋 Thanks for opening your first pull request. A contributor should give feedback soon. If you haven’t already, please check out the contributing guidelines.

[alex-page]

This is great @malanjp, one suggestion.

[BPScott]

array.includes is pretty ubiquitous these days. What do you think to using that instead?

validImageTypes.includes(file.type)

[malanjp]

How to pass CI/Visual regression test?

Chromatic CLI v5.5.0
chromatic.com/docs/cli

✖ Missing project token

Sign in to chromatic.com/start and create a new project,
or find your project token on the Manage screen in an existing project.
Set your project token as the CHROMATIC_PROJECT_TOKEN environment variable
or pass the --project-token command line option.

ℹ Read more at chromatic.com/docs/setup
Error: non-zero exit code

[ghost]

🎉 Thanks for your contribution to Polaris React!

[alex-page]

Thankyou @malanjp ✨