I have created a Tampermonkey userscript that will enable keyboard shortcuts in codeforces website. Here is a brief description

On a problem statement page,

• Pressing 's' will open a new tab going to the submit page and automatically select the problem number
• Pressing 's' again will copy the content of your clipboard, paste it in the source code area then click the submit button
• So, submission is now two key presses (or three, sometimes you need to focus the submit page first with a keypress or mouse click)

Extras

• Change font size in the problem statement page
• Press 'R' to go to contest ranking page with friends=true

The repo contains a short demo as well

All of the keybindings and font size can be customized

Suggestions of other shortcuts that may be useful is appreciated

Note: Automatic pasting of clipboard content is not supported in firefox