Feature request: add jam form

[cxong]

Adding jams is really fiddly. Pull requests are fine, but then you have to navigate to the JSON, and manually edit it in a text editor.

I'd suggest having a HTML form which outputs a valid JSON block, which the user can then paste into the pull request.

[leafo]

I do have this form: https://docs.google.com/forms/d/1c2UrXfRdJm723fv7kJY0BG7eOCg8nC9eNp-fARe6aqE/viewform

But I think a form that outputs json great idea and will simplify things for me, I'll look in to creating something.

[0x0961h]

@leafo What's the output of this form? Google Docs' table?