Added 'Accept: application/json' to the fetch headers which causes Slim
to return errors as JSON so we can output the errors nicely.

Added --no-hmr to the parcel watch because it's not working and I don't
want to spend time to figure it out right now.

Moved all the Javascript in donate-form out of the div that gets used
for the React component because that gets entirely replaced by the React
component which has been working, but I think it's weird and for
debugging its nicer if you can see the original Javascript in the DOM in
the browser.