UART is missing timeout parameter

[couillonnade]

Hello,

UART is missing timeout parameter in RP2 port.

The parameter is in the documentation here: https://docs.micropython.org/en/latest/library/machine.UART.html#machine-uart

There are other missing parameters that I am not sure apply to RP2:

rts specifies the RTS (output) pin to use for hardware receive flow control.
cts specifies the CTS (input) pin to use for hardware transmit flow control.
txbuf specifies the length in characters of the TX buffer.
rxbuf specifies the length in characters of the RX buffer.
timeout specifies the time to wait for the first character (in ms).
timeout_char specifies the time to wait between characters (in ms).
invert specifies which lines to invert.

Generally speaking I am not sure how to know what apply to specific port, like RP2, without testing on the board but the doc suggest that all those parameters apply.

Also not sure if you accept Pull Request and if you have some documentation for contributions.