Add github action for SwiftLint

.github/workflows/swiftlint.yml

@@ -0,0 +1,18 @@
+name: SwiftLint
+
+on:
+  pull_request:
+    paths:
+      - '.github/workflows/swiftlint.yml'
+      - '.swiftlint.yml'
+      - '**/*.swift'
+
+jobs:
+  SwiftLint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - name: GitHub Action for SwiftLint (Only files changed in the PR)
+        uses: norio-nomura/action-swiftlint@3.2.1
+        env:
+          DIFF_BASE: ${{ github.base_ref }}