Add ADC example to workflow

Author: ajaybhargav

.github/workflows/examples.yml

@@ -11,6 +11,7 @@ jobs:
         python-version: [3.7]
         example:
           - "examples/gpio-blink"
+          - "examples/adc-example"
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v2