Added platformio.ini, moved test.cpp into src dir. Builds/runs (#32)

Author: skiphansen

example/README.md

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+## Building the example
+
+### Requirements
+
+1. A system running Linux or Linux running in a VM.
+2. gcc (`sudo apt-get install build-essential` or equivalent).
+3. gpiod and libgpiod-dev library (`sudo apt-get install gpiod libgpiod-dev` or equivalent).
+4. libbluetooth-dev library (`apt-get install libbluetooth-dev` or equivalent).
+5. PlatformIO. See https:/platformio.org/install for instruction instructions.
+
+Once all of the requirements have been met go into the example subdirectory
+and run platform IO to build the example.
+
+For example:
+
+```
+skip@Dell-7040:~../resources/framework-portduino$ cd example/
+skip@Dell-7040:~../resources/framework-portduino/example$ git submodule init
+Submodule 'libraries/WiFi' (https:/github.com/Meshtastic/WiFi.git) registered for path '../libraries/WiFi'
+skip@Dell-7040:~../resources/framework-portduino/example$ git submodule update
+Cloning into '/home/skip../resources/framework-portduino/libraries/WiFi'...
+Submodule path '../libraries/WiFi': checked out 'b885b9595d54ee6eae59696eeae98f631eb27a23'
+skip@Dell-7040:~../resources/framework-portduino/example$ pio run
+Processing native (platform: https:/github.com/meshtastic/platform-native.git; framework: arduino; board: linux_hardware)
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+Verbose mode can be enabled via `-v, --verbose` option
+CONFIGURATION: https:/docs.platformio.org/page/boards/native/linux_hardware.html
+PLATFORM: Native (1.2.1+sha.04435d0) > Portduino
+HARDWARE: 95.37MB RAM, 95.37MB Flash
+PACKAGES:
+ - framework-portduino @ 0.0.1+sha.de3548f
+LDF: Library Dependency Finder -> https:/bit.ly/configure-pio-ldf
+LDF Modes: Finder ~ chain, Compatibility ~ soft
+[nanopb] Installing Protocol Buffers dependencies
+Requirement already satisfied: protobuf>=3.19.1 in /home/skip/.platformio/penv/lib/python3.8/site-packages (4.25.2)
+
+... (lots of output deleted) ...
+
+Compiling .pio/build/native/FrameworkArduino/portduino/simulated/SimHardwareSPI.cpp.o
+Archiving .pio/build/native/libFrameworkArduino.a
+Indexing .pio/build/native/libFrameworkArduino.a
+Linking .pio/build/native/program
+================================================================================== [SUCCESS] Took 1.99 seconds ==================================================================================
+skip@Dell-7040:~../resources/framework-portduino/example$
+```
+

example/platformio.ini

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+[platformio]
+default_envs = native
+
+[env:native]
+platform = https://github.com/meshtastic/platform-native.git
+build_flags = ${env.build_flags} -O0
+framework = arduino
+board = linux_hardware
+
+
+
+