Changes to the create new pull request page

[joeytwiddle]

Edit: I have just realised that I have posted in the wrong repo! I should have posted here. I have no idea if the same problem applies to this project or not!

Github recently made some small changes to the page we use to open a new pull request.

As a result, the text box is no longer wide, and sits on the far left, leaving a big empty gap on the right hand side.

I had a little play with the CSS but it didn't look that trivial to solve, so I'm hoping one of you experts can do it... :)

(I am actually using the userscript release here.)