Fix event-read-char-line example double read error & auto enter

[hthuz]

I tried following the example in event-read-char-line to read keyboard character event without having to press enter. I met some problems when I tried this example.

The first problem is double key input in Windows. I tracked issue #772 and it turns out kind: KeyEventKind::Press is not added when reading event in this example.

The second problem is with read_line() function. It seems that it captures the pressed Enter command when I run cargo run --example event-read-char-line.

The third problem is, I have to press Enter for read_char() to get my keyboard input in WSL.

I played with this example for some time and compared with other examples. I made some modifications and they should fix these problems. For read_line(), I don't know exactly why the original while doesn't work but replacing it with loop does solve the second problem.

[hthuz]

Hi @TimonPost could you review it when you have a chance? I'd appreciate your comments and feedbacks. Thank you!