Smoke test uppy.io on CI deploy

[mifi]

Initial checklist

• I understand this is a feature request and questions should be posted in the Community Forum
• I searched issues and couldn’t find anything (or linked relevant results below)

Problem

We have sometimes been surprised that uppy.io has been broken without us knowing

Solution

Create a simple smoke test (browser test?) of for example uploading a file from an URL - which will hit the multiple Companion instances.

Because uppy.io now runs with two instances of companion behind a load balancer, this will make sure that companion works properly with multiple instances (which is hard to forget to check when developing locally)

Alternatives

Make a functional test as part of the test suite, but then we need to do a lot of extra configuring and setting up a local load balancer etc, so a smoke test could be a shortcut. See also #3538

[Murderlon]

I think we can close this as we're close to a new website in a different repository, which AFAIK will be rebuild on new releases, which are far more likely to be stable. Alternatively, we transfer this issue to that repo and create an e2e test.

[arturi]

I am for this independent test that just tests Uppy.io and annoyingly emails me if it fails to upload via URL. I can look into implementing this.