Add GitHub Actions workflow for automated compilation testing

- Add GitHub Actions workflow in .github/workflows/compile-test.yml.
- Configure Arduino CLI to use Earle Philhower's RP2040 core.
- Automatically compile all .ino examples on every push and pull request.
- Ensure library integrity against the RP2040:rpipico board architecture.

Author: jit89

.github/workflows/compile-test.yml

@@ -0,0 +1,35 @@
+name: Compile Check
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout Code
+        uses: actions/checkout@v3
+
+      - name: Install Arduino CLI
+        run: |
+          curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | sh
+          echo "$HOME/bin" >> $GITHUB_PATH
+
+      - name: Setup RP2040 Core
+        run: |
+          arduino-cli core update-index
+          arduino-cli core update-index --additional-urls https://github.com/earlephilhower/arduino-pico/releases/download/global/package_rp2040_index.json
+          arduino-cli core install rp2040:rp2040 --additional-urls https://github.com/earlephilhower/arduino-pico/releases/download/global/package_rp2040_index.json
+
+      - name: Link Library
+        run: |
+          mkdir -p $HOME/Arduino/libraries
+          ln -s $GITHUB_WORKSPACE $HOME/Arduino/libraries/PicoTimer
+
+      - name: Compile Examples
+        run: |
+          # This compiles every .ino file found in the examples folder
+          for example in $(find ./examples -name "*.ino"); do
+            echo "Compiling $example..."
+            arduino-cli compile --fqbn rp2040:rp2040:rpipico $example
+          done