I wrote a TFS/VSTS extension and decided to open source it. Check it out at https://marketplace.visualstudio.com/items?itemName=mike-branstein.board-form-control.
Help your team move work items on the board from the work item form’s context menu
The source for this extension can be found on Github – feel free to take, fork and extend.
You can also learn how to build your own custom control extension for the work item form here.