STDIN doesn't seem to be working in WSL2

[weikinhuang]

Hi, this is an awesome script, I'm having an issue with using stdin in WSL 2 with the elevated sessions.

The following example will hang, I'm expecting an output of 123 like if I run it in a normal shell echo 123 | cat -.

echo 123 | python3 wsl-sudo.py cat -

This outputs 123 in WSL 1, but then hangs after.

Thanks for taking a look.

[kajic]

@weikinhuang Here's a fix for this issue: #10