chore: add stylua to format the codebase, and run on CI (#1055)

.github/workflows/ci.yml

@@ -0,0 +1,34 @@
+name: CI
+
+on:
+  pull_request:
+    branches:
+      - '*'
+  push:
+    branches:
+      - master
+
+jobs:
+  luacheck:
+    name: luacheck
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Prepare
+        run: |
+          sudo apt-get update
+          sudo add-apt-repository universe
+          sudo apt install luarocks -y
+          sudo luarocks install luacheck
+      - name: Run luacheck
+        run: luacheck .
+  stylua:
+    name: stylua
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: JohnnyMorganz/stylua-action@1.0.0
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          args: --color always --check lua/