It would be handy to be able to edit the keys and/or values of the existing HTTP headers, without having to delete and re-enter both key and value.

I'm trying to add this feature on my own fork, but I haven't been able to get the app to start yet. I managed to get it building by npm linking to a freshly cloned graphiql repository but the app throws an error when it trying to load the QueryEditor. Not sure what I'm doing wrong, any idea how I could work around that?