Add .pre-commit-config.yaml to have auto clang-format

It's only enabled when `pre-commit install` is issued
and will make sure the changed code has the correct
style with clang-format v12.0.1

.pre-commit-config.yaml

@@ -0,0 +1,13 @@
+# See https://pre-commit.com for more information
+# See https://pre-commit.com/hooks.html for more hooks
+exclude: ^(cmake/)
+repos:
+- repo: https://github.com/pre-commit/pre-commit-hooks
+  rev: v4.6.0
+  hooks:
+  - id: trailing-whitespace
+  - id: end-of-file-fixer
+- repo: https://github.com/pre-commit/mirrors-clang-format
+  rev: v12.0.1
+  hooks:
+  - id: clang-format