fix: await flush files when using --watch mode

[koba04]

Fixes #103

#103 caused by emitting a file change event before flushing a disk.
In order to fix that, I use awaitWriteFinish option of chokidar.

https://github.com/paulmillr/chokidar#performance

I set 1000ms as the stabilityThreshold, of which default value is 2000ms though.
Because 2000ms is a bit long in our cases.
In my windows environment, 500ms also works fine but it depends on changes and device specs so I chosen 1000ms as the value safely.

[teppeis]

@koba04 Thank you!
This change makes Mac/Linux user's experience worse too.
Can you limit this change only for Windows?

[koba04]

@teppeis
Thank you for your review! I'm not sure this behavior is only on Windows.
But it might be good to limit this change only for Windows as you mentioned. We could add it later if this happened on Mac or Linux.

I'll work on it.

[koba04]

@teppeis

Can you limit this change only for Windows?

I've addressed it.