Implement bitflag check for event key event flags.

[TimonPost]

related: #20

According to windows documentation:

[in] dwFlags
Controls various aspects of mouse motion and button clicking. This parameter can be certain combinations of the following values.

Currently, there are only checks to check against one particular case (see this file)

impl From<DWORD> for EventFlags {
    fn from(event: DWORD) -> Self {
        match event {
            0x0000 => EventFlags::PressOrRelease,
            0x0002 => EventFlags::DoubleClick,
            0x0008 => EventFlags::MouseHwheeled,
            0x0001 => EventFlags::MouseMoved,
            0x0004 => EventFlags::MouseWheeled,
            _ => panic!("Event flag {} does not exist.", event),
            _ => EventFlags::Unknown,
        }
    }

Ideally, we need to be able to detect all cases.

This also impacts: https://github.com/crossterm-rs/crossterm/blob/master/src/event/sys/windows/parse.rs#L143

And we need to find a way to handle it there as well.

[sigmaSd]

EventFlags need to be a bitflag struct, and the varient const instance

I think that should be ok and https://github.com/crossterm-rs/crossterm/blob/master/src/event/sys/windows/parse.rs#L143 can use contains to see if a flag is set

The only probem I see is that https://github.com/crossterm-rs/crossterm/blob/master/src/event/sys/windows/parse.rs#L143 can now return a vector of events, how do you see handling this?

[sigmaSd]

Basicly the question is should https://github.com/crossterm-rs/crossterm/blob/master/src/event.rs#L349 also be a bitflag struct?

If so this would make it easy to fix this issue

[sigmaSd]

Or a simpler thing is to make the kind field in mouse event a vector of mouseeventkind

Also Im not sure if linux can benefit from this

[sigmaSd]

@TimonPost I just noticed the msdoc page that you linked is for winapi https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-mouse_event

I think the correct page is https://docs.microsoft.com/en-us/windows/console/mouse-event-record-str#members which doesn't mention that it possible to combine values