pre-commit: add mixed-line-ending hook [skip ci]

.pre-commit-config.yaml

@@ -7,6 +7,7 @@ repos:
       - id: end-of-file-fixer
       - id: trailing-whitespace
       - id: check-merge-conflict
+      - id: mixed-line-ending
   - repo: https://github.com/pre-commit/mirrors-clang-format
     rev: v15.0.7
     hooks: