chore(sonar): add github action to scan code

.github/workflows/sonar-scan.yml

@@ -0,0 +1,22 @@
+name: Sonar Scan
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+jobs:
+  sonarcloud:
+    name: SonarCloud
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0  # Shallow clones should be disabled for a better relevancy of analysis
+      - name: SonarCloud Scan
+        uses: SonarSource/sonarcloud-github-action@master
+        env:
+          GITHUB_TOKEN: ${{ secrets.GH_TOKEN }}  # Needed to get PR information, if any
+          SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}

sonar-project.properties

@@ -0,0 +1,4 @@
+sonar.organization=react-native-datetimepicker
+sonar.projectKey=datetimepicker
+sonar.sources=src
+sonar.sourceEncoding=UTF-8