Update WebDriver installation instructions for WSL

[cai-lw]

oj/onlinejudge_command/subcommand/login.py

Lines 109 to 111 in ec4b743

	If you use Ubuntu under Windows Subsystem for Linux:
	1. Make a symbolic link from cookie.jar in WSL to cookie.jar out of WSL. For example, run $ ln -s /mnt/c/Users/%USERNAME%/AppData/Local/online-judge-tools/online-judge-tools/cookie.jar /home/ubuntu/.local/share/online-judge-tools/cookie.jar
	2. Use `oj login` outside of WSL

WSL now supports GUI applications by default. No setup is needed. There should be commands that work for both native Ubuntu and Ubuntu in WSL. Or at least there is no need to oj login on Windows.

I personally installed Google Chrome following https://learn.microsoft.com/en-us/windows/wsl/tutorials/gui-apps#install-google-chrome-for-linux and then ChromeDriver from https://chromedriver.chromium.org, and it worked well. I couldn't make Chromium work and haven't tried other browsers. However since Google Chrome is for-profit, proprietary software we may not want to advertise it in this free, open-source project. If we find a free browser that works in WSL, we should update the instructions to use that.