Update i2c-lcd1602.c

[JacksonJoseG]

i2c_lcd1602_write_string() modified:
Automatically moves to second line if a '\n' char is detected.

[DavidAntliff]

Thanks for the PR.

This component also works with the LCD2004 module (4 lines). Before I can merge this, can you consider what happens with the 4-line display, please? It would need to advance the "cursor" (i.e. place where the next character would appear) to the next line, rather than line 2.

Also, consider what would happen if the cursor was on the last line of the display. Should it jump back to the top? Or should the entire display scroll up and new characters appear on the bottom line? Or maybe it just stays on the bottom line but moves to the far left?

These questions are why I kept the newline behaviour explicit for now (as in, handle it yourself, outside the library), as different users may have different requirements or expectations.