ar_flush_hard: Flush serial port in the hard way
In hebrewseniorlife/arduinor: Simple Library for Reading Serial Ports

In theory ar_flush should work but it didn't work out for me at least. So I recreated this flush feature in R, which basically let the data flow for a short time (default 50 ms). The selection of this value depends of many factors including the USB port and the size of data so please pick this value wisely.

1	ar_flush_hard(fd, flush_time = 0.05, include_c_flush = TRUE)

`fd`	File descriptor returned by `ar_init()`. Should be an integer.
`flush_time`	Time to flush buffed results in the serial channel
`include_c_flush`	T/F for whether to call ar_flush at the beginning