Add CI workflow to do Arduino project-specific linting

On every push, pull request, and periodically, run Arduino Lint to check for common problems not related to the project
code.

Author: per1234

Diff for: .github/workflows/check-arduino.yml

@@ -0,0 +1,28 @@
+name: Check Arduino
+
+# See: https://docs.github.com/en/free-pro-team@latest/actions/reference/events-that-trigger-workflows
+on:
+  push:
+  pull_request:
+  schedule:
+    # Run every Tuesday at 8 AM UTC to catch breakage caused by new rules added to Arduino Lint.
+    - cron: "0 8 * * TUE"
+  workflow_dispatch:
+  repository_dispatch:
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Arduino Lint
+        uses: arduino/arduino-lint-action@v1
+        with:
+          compliance: specification
+          library-manager: update
+          # Always use this setting for official repositories. Remove for 3rd party projects.
+          official: true
+          project-type: library

Diff for: README.adoc

@@ -4,6 +4,7 @@
 
 = Modbus Library for Arduino =
 
+image:https://github.com/{repository-owner}/{repository-name}/actions/workflows/check-arduino.yml/badge.svg["Check Arduino status", link="https://github.com/{repository-owner}/{repository-name}/actions/workflows/check-arduino.yml"]
 image:https://github.com/{repository-owner}/{repository-name}/actions/workflows/compile-examples.yml/badge.svg["Compile Examples status", link="https://github.com/{repository-owner}/{repository-name}/actions/workflows/compile-examples.yml"]
 image:https://github.com/{repository-owner}/{repository-name}/actions/workflows/spell-check.yml/badge.svg["Spell Check status", link="https://github.com/{repository-owner}/{repository-name}/actions/workflows/spell-check.yml"]