Fix UnicodeDecodeError when running yamllint under certain Windows code pages

[tahakiziltepe]

This PR addresses an issue where running yamllint (via pre-commit) on Windows with a non-UTF-8 code page (like CP1254) could trigger a UnicodeDecodeError. The problem occurred because yamllint was attempting to read and decode the file contents using the default system encoding, which didn’t properly handle certain characters.

Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "C:\<pyenv>\Scripts\yamllint.EXE\__main__.py", line 7, in <module>   
  File "C:\<pyenv>\Lib\site-packages\yamllint\cli.py", line 223, in run     
    problems = linter.run(f, conf, filepath)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\<pyenv>\Lib\site-packages\yamllint\linter.py", line 232, in run  
    content = input.read()
              ^^^^^^^^^^^^
  File "C:\<python>\Lib\encodings\cp1254.py", line 23, in decode
    return codecs.charmap_decode(input,self.errors,decoding_table)[0]
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
UnicodeDecodeError: 'charmap' codec can't decode byte 0x8f in position 296: character maps to <undefined>

To fix this, I updated the file-reading logic to:

• Check if input.encoding is set and if it’s neither UTF-8 nor buffer.
• If so, read from input.buffer directly.
• Otherwise, read and decode with UTF-8.

And it worked well:

Thanks for reviewing.