Added workflow for formatting (#102)

.github/workflows/format.yml

@@ -0,0 +1,30 @@
+name: format
+
+on:
+  pull_request:
+    branches:
+      - "master"
+
+jobs:
+  stylua:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup and run stylua
+        uses: JohnnyMorganz/stylua-action@1.0.0
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          args: --config-path=./.stylua.toml -g *.lua -g !*.spec.lua -- .
+      - name: Commit files
+        run: |
+          git config --local user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git config --local user.name "github-actions[bot]"
+          if [[ ! -z $(git status -s) ]]; then
+            git add .
+            git commit -m "Auto: format source code"
+          fi
+      - name: Push formatted files
+        uses: ad-m/github-push-action@master
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          branch: ${{ github.ref }}

.stylua.toml

@@ -0,0 +1,6 @@
+column_width = 80
+line_endings = "Unix"
+indent_type = "Spaces"
+indent_width = 4
+quote_style = "AutoPreferDouble"
+no_call_parentheses = false