Disable issue creation form while waiting for xhr request to finish

この issue には説明がありません。

The issue lacks a description, so first examine the codebase to locate the issue creation form and the XHR request handling. Look for Elm modules related to forms and HTTP requests. Determine how to disable the form during an XHR request, likely by managing a boolean flag in the model and updating the view accordingly. Check for existing patterns in the code for handling loading states.

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