ci: GHA basic format & pre-commit (#2309)

diff --git a/tools/mkdoc.py b/tools/mkdoc.py
index cd982e0..a22aacd 100755
--- a/tools/mkdoc.py
+++ b/tools/mkdoc.py
@@ -1,4 +1,5 @@
 #!/usr/bin/env python3
+# -*- coding: utf-8 -*-
 #
 #  Syntax: mkdoc.py [-I<path> ..] [.. a list of header files ..]
 #