Add CI workflow to compile example sketches

On every push and pull request, do a "smoke test" by compiling the example sketches of the library for the given list of
Arduino boards.

Author: per1234

.github/workflows/compile-examples.yml

@@ -0,0 +1,80 @@
+name: Compile Examples
+
+on:
+  pull_request:
+    paths:
+      - ".github/workflows/compile-examples.yml"
+      - "examples/**"
+      - "src/**"
+  push:
+    paths:
+      - ".github/workflows/compile-examples.yml"
+      - "examples/**"
+      - "src/**"
+  schedule:
+    # run every Tuesday at 3 AM UTC to catch breakage caused by changes to external dependencies (libraries, platforms)
+    - cron: "0 3 * * 2"
+  # See: https://docs.github.com/en/free-pro-team@latest/actions/reference/events-that-trigger-workflows#workflow_dispatch
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    env:
+      # Libraries to install for all boards
+      UNIVERSAL_LIBRARIES: |
+        # Install the ArduinoModbus library from the local path
+        - source-path: ./
+        - name: ArduinoRS485
+      UNIVERSAL_SKETCH_PATHS: |
+        - examples/RTU
+
+    strategy:
+      fail-fast: false
+
+      matrix:
+        board:
+          - fqbn: arduino:avr:nano
+            nina: false
+          - fqbn: arduino:avr:leonardo
+            nina: false
+          - fqbn: arduino:megaavr:uno2018:mode=off
+            nina: true
+          - fqbn: arduino:samd:mkrwifi1010
+            nina: true
+          - fqbn: arduino:mbed:nano33ble
+            nina: false
+          - fqbn: arduino:mbed:envie_m7
+            nina: false
+
+        # Make board type-specific customizations to the matrix jobs
+        include:
+          - board:
+              # Boards with NINA-W102 module
+              nina: true
+            # Install these libraries in addition to the ones defined by env.UNIVERSAL_LIBRARIES
+            nina-libraries: |
+              - name: WiFiNINA
+            # Compile these sketches in addition to the ones defined by env.UNIVERSAL_SKETCH_PATHS
+            nina-sketch-paths: |
+              - examples/TCP
+          - board:
+              nina: false
+            nina-libraries: ""
+            nina-sketch-paths: ""
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Compile examples
+        uses: arduino/compile-sketches@main
+        with:
+          fqbn: ${{ matrix.board.fqbn }}
+          libraries: |
+            ${{ env.UNIVERSAL_LIBRARIES }}
+            ${{ matrix.nina-libraries }}
+          sketch-paths: |
+            ${{ env.UNIVERSAL_SKETCH_PATHS }}
+            ${{ matrix.nina-sketch-paths }}

README.adoc

@@ -1,5 +1,11 @@
+// Define the repository information in these attributes
+:repository-owner: arduino-libraries
+:repository-name: ArduinoModbus
+
 = Modbus Library for Arduino =
 
+image:https://github.com/{repository-owner}/{repository-name}/workflows/Compile%20Examples/badge.svg["Compile Examples Status", link="https://github.com/{repository-owner}/{repository-name}/actions?workflow=Compile+Examples"]
+
 Use http://www.modbus.org/[Modbus] with your Arduino. 
 
 Using TCP or RS485 shields, like the MKR 485 Shield. This library depends on the ArduinoRS485 library.