Kattis UI Fix

Adds back the old Kattis UI buttons on problem pages as well as a toggle to hide the editor panel.

Kattis recently overhauled their UI, and in the new wave of changes two very important buttons were unfortunately removed: the "My Submissions" and "Statistics" buttons on each problem's page. But no more! With this extension, these buttons will come back better than ever! You will be able to finally feel more familiar with the new Kattis design, as we all know that UI overhauls can be difficult and trying times. Additionally, this extension adds a "Toggle Editor" button to toggle viewing/hiding the new code editor panel. Now you can view the problem description in it's full form (which hopefully results in more AC and less WA). Updates: June 22, 2022 Update - Added ability to see the statistics and toggle button even when not signed in - Added a difficulty row to the problem page and options to sort problems by users instead of submissions like in the old Kattis, thanks to Hazem !! July 11, 2022 Update - Kattis added back the difficulty row on the problem page so the extra one is now redundant - Added the sort buttons to problem sources and problem authors pages - Fixed some small errors July 20, 2022 Update - Support for problem pages on subdomains like https://nac22.kattis.com/ August 14, 2022 Update - Fixed a bug with the toggle editor button not working properly.