fix: make sure output file directory exists before trying to open file for writing. Fixes #13 (#14)

Co-authored-by: Andreas Kunze <andreas.kunze@watttron.com>

Author: and2345

pybind11_mkdoc/mkdoc_lib.py

@@ -420,6 +420,7 @@ def mkdoc(args, width, output=None):
 
     if output:
         try:
+            os.makedirs(os.path.dirname(output), exist_ok=True)
             with open(output, 'w') as out_file:
                 write_header(comments, out_file)
         except: