Add delays to avoid corrupting packages.

[Magic-Doufu]

Add delays to solve corruption pack issue. (CH341 working well, but ft232 with vcp driver always corrupting.)

-->1-3-0-0-0-10-197-205
<--1-3-20-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-163-103
-->1-3-0-0-0-10-197-205
<--1-3-20-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-163-103
-->1-3-0-0-0-10-197-205
<--1-3-20-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-163-103
-->1
invalid request: Request length is invalid 1
-->3-0-0-0-10-197-205
invalid request: Invalid CRC in request

[jacksonmatheson]

"For use with FT232-RS485 device"???

But it's sitting under a while True and will affect every modbus_rtu device.

This will halt all execution for every modbus-rtu device prior to reading the rest of a request, a completely unessesary performance impact for many applications which do not warrant it.

I've had projects pushing near 500 requests per second, and i wouldn't be suprised if others are pushing higher, even if just in bench tests a 0.001s delay is massive in that regard.