workflow: Add github action for coding style checking

Download clang-format-diff.py from LLVM project and run the script
for changes between main and HEAD.

Signed-off-by: Hyeonggon Yoo <[email protected]>

.github/workflows/CI.yml

@@ -0,0 +1,23 @@
+# This is a basic workflow to help you get started with Actions
+name: CI
+
+# Controls when the workflow will run
+on: [push, pull_request, workflow_dispatch]
+
+# A workflow run is made up of one or more jobs that can run sequentially or in parallel
+jobs:
+  # This workflow contains a single job called "build"
+  build:
+    # The type of runner that the job will run on
+    runs-on: ubuntu-latest
+
+    # Steps represent a sequence of tasks that will be executed as part of the job
+    steps:
+      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
+      - uses: actions/checkout@v3
+      # Runs a set of commands using the runners shell
+      - name: Download clang-format-diff.py that checks coding style
+        run:  wget https://raw.githubusercontent.com/llvm/llvm-project/main/clang/tools/clang-format/clang-format-diff.py
+      - name: Run clang-format-diff.py
+        run: git diff -U0 --no-color origin/main HEAD | python3 ./clang-format-diff.py -p1
+      # TODO: Run testcases for LLVM pass