Add contributing section to README.

README.md

@@ -1,23 +1,40 @@
 # GPS for Flipper Zero
 
-A simple Flipper Zero application for NMEA 0183 serial GPS modules, such as the [Adafruit Ultimate GPS Breakout].
+A simple Flipper Zero application for NMEA 0183 serial GPS modules, such as the
+[Adafruit Ultimate GPS Breakout].
 
 ![ui](ui.png)
 
-Heavy lifting (NMEA parsing) provided by [minmea], which is included in this repository.
+Heavy lifting (NMEA parsing) provided by [minmea], which is included in this
+repository.
 
 ## Hardware Setup
 
-Connect the GPS module to power and the USART using GPIO pins 9 (3.3V), 11 (GND), 13 (TX), and 14 (RX), as appropriate.
+Connect the GPS module to power and the USART using GPIO pins 9 (3.3V), 11
+(GND), 13 (TX), and 14 (RX), as appropriate.
 
 ![wiring](wiring.png)
 
 ## Building the FAP
 
 1. Clone the [flipperzero-firmware] repository.
-2. Create a symbolic link in `applications_user` named `gps`, pointing to this repository.
+2. Create a symbolic link in `applications_user` named `gps`, pointing to this
+   repository.
 3. Compile with `./fbt fap_gps`.
-4. Copy `build/f7-firmware-D/.extapps/gps.fap` to `apps/Tools` on the SD card (directly or using [qFlipper]).
+4. Copy `build/f7-firmware-D/.extapps/gps.fap` to `apps/Tools` on the SD card
+   (directly or using [qFlipper]).
+
+## Contributing
+
+This project was a learning exercise and is more or less "complete" from my
+perspective, but I will happily accept pull requests that improve and enhance
+the functionality for others.
+
+Currently, the app only parses RMC and GGA sentences, and displays a subset of
+the data that fits on the screen. The UART is also hard-coded to 9600 baud.
+These limitations are largely driven by the GPS module I have to work with. A
+more elaborate UI with scrolling or multiple screens, as well as a configurable
+baud rate, may be useful for other GPS modules.
 
 [Adafruit Ultimate GPS Breakout]: https://www.adafruit.com/product/746
 [minmea]: https://github.com/kosma/minmea