Added function soft Reset + extended begin function with new parameters (as clone of begin function)

[gauner666]

Hello, the following commit does these 2 things:

1. Added support for softReset, where the sensor will simply soft-reset itself (like described in the manual. Tested on R503, working). I did this because my R503 sensor (one of three) is stopping to work after a couple of months. A power cycle solved the issue. The new function resets the sensor as it would be with a power cycle.
2. Added new function begin which is a clone of your begin function but extends it with 2 parameters: rx, tx. These 2 integers are the ports, the sensor is attached to.

There is no breaking change.
There is no limitation in this change.

Actually working in production, tests were made.

[gauner666]

PS: Seems that there are issues on function call begin with tx,rx for software serial.
Did the test on ESP32 ATOM M5 (various versions, also S3) which are HardwareSerial