Add clang-format ci (#524)

* Add clang-format ci

* format
Co-authored-by: Farhad Ramezanghorbani <farhadrgh@users.noreply.github.com>

.github/workflows/clang-format.yml

+name: clang-format
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+  schedule:
+    - cron: '0 0 * * *'
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v1
+    - name: Lint with clang-format
+      run: |
+        find -name '*.cpp' -o -name '*.h' -o -name '*.cu' -o -name '*.cuh' | xargs clang-format -i
+        GIT_DIFF=$(git diff)
+        if [[ -z $GIT_DIFF ]]; then
+            exit 0
+        fi
+        echo $GIT_DIFF
+        exit 1

torchani/cuaev/delete-me.cu

+// This file only exists temporarily for validating the clang-format CI
+// This file should be deleted when https://github.com/aiqm/torchani/pull/516
+// or https://github.com/aiqm/torchani/pull/521 is merged.
+
+#include <stdio.h>
+#include <stdlib.h>
+
+__global__ void print_from_gpu(void) {
+  printf("Hello World! from thread [%d,%d] \
+        From device\n",
+         threadIdx.x, blockIdx.x);
+}
+
+int main(void) {
+  printf("Hello World from host!\n");
+  print_from_gpu<<<1, 1>>>();
+  cudaDeviceSynchronize();
+  return 0;
+}