Allow upload tags as array

[harrygr]

Tags can be provided as an array rather than a comma-separated string as FormData will coerce it.

const form = new FormData()
form.append('tags', ['a', 'b'])
Object.fromEntries(form)
// Object { tags: "a,b" }
``

[harrygr]

It looks like the type definition of Form.prototype.append only allows strings and Blobs so, even though passing a string[] does work it's not technically compliant with the api. Closing...