Adds GitHub Action that builds the arduino examples. (#534)

This Action works as a CI ensuring that the Arduino OpenMRNLite library and its contributed examples are building correctly.

The Action triggers automatically upon every pull request, and builds all ESP32*.ino and Stm32*.ino sketches using arduino-cli. The OpenMRNLite library and the example sketches are always taken from HEAD.

An example run is visible here:
https://github.com/balazsracz/openmrn/runs/2314541629?check_suite_focus=true

===

* Adds a workflow to build the ESP32 arduino examples.

* upgrade version

* fix indent

* Add libify to build action

* fix paths

* Add STM32 compilation step

* fix typo in sketch names

* update stm32 target

* try deleting the build opt

* add compile flag

* Fix format

* Revert "try deleting the build opt"

This reverts commit 3692abb.

* Patch remove the build_opt.h files.
build all stm32 examples.

* Adjust when to run

* Update esp32 platform URL to point to their github.

.github/workflows/ArduinoBuild.yml

@@ -0,0 +1,49 @@
+# ArduinoBuild.yml
+#
+# Github workflow script that compiles all examples from the OpenMRNLite
+# Arduino library.
+#
+# Copyright (C) 2021  Balazs Racz
+#
+
+# Name of workflow
+name: ArduinoBuild
+on:
+  push:
+    paths:
+      - '**.ino'
+      - '**rduino**'
+      - '**ArduinoBuild.yml'
+  pull_request:
+jobs:
+  build:
+    name: Build ESP32 examples
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@master
+
+    - name: Generate OpenMRNLite library
+      run: |
+        mkdir --parents $HOME/Arduino/libraries/OpenMRNLite
+        $GITHUB_WORKSPACE/arduino/libify.sh $HOME/Arduino/libraries/OpenMRNLite $GITHUB_WORKSPACE -f -l
+        rm -f $GITHUB_WORKSPACE/arduino/examples/Stm*/build_opt.h
+
+    - name: Compile all STM32 examples
+      uses: ArminJo/[email protected]
+      with:
+        platform-url: https://raw.githubusercontent.com/stm32duino/BoardManagerFiles/master/STM32/package_stm_index.json
+        arduino-board-fqbn: STM32:stm32:Nucleo_144:pnum=NUCLEO_F767ZI,upload_method=MassStorage,xserial=generic,usb=CDCgen,xusb=FS,opt=osstd,rtlib=nano
+        sketch-names: Stm32*.ino
+        build-properties: '{ "All": "-DHAL_CAN_MODULE_ENABLED" }'
+        debug-compile: true
+
+    - name: Compile all ESP32 examples
+      uses: ArminJo/[email protected]
+      with:
+        platform-url: https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json
+        arduino-board-fqbn: esp32:esp32:node32s
+        sketch-names: ESP*.ino
+        debug-compile: true
+
+