Add listen function for external call.

[asas1asas200]

I have added a listen function to call the internal listen function of _serial.

If I use Arduino UNO, I can only use one SoftwareSerial at a time.
And the SoftwareSerial.listen() function can help us to switch between multiple serials.
Add this feature for more flexibility.

[arduino12]

Thanks for your explanation and great work!
Please also add them to the keywords file as well,
Also it will be nice to keep the original conventions and call it is_listening but it is your choice :)
Will merge after your next commit :)

[arduino12]

Also if you have the time to add a simple example demonstrating the use of these function for me and others to see it will be super nice 🥇 maybe create 2 Rdm6300 instances for example?

[asas1asas200]

I have added an example for it!
And I didn't notice the class member transition of _serial because I read the release version, but it's fixed now.

[arduino12]

Great work @asas1asas200 !
Thanks..!

[arduino12]

@JessicaWoods03
They comes with the Arduino core environment,
Just google "arduino stream.h" and find them on the Arduino repo.

Also,
This is not the place to ask such questions that are not related to this pull request..

[JessicaWoods03]

Oh, sorry...this is the site I am directed to when I am working with rdm_6300...it continues to come back to this site, I am new to using Arduino's.....he has three header files listed on his header that I was not familiar with as far as were to get those-