text: Title: [BUG] sktime has codec error in Windows 11 Traditional Chinese System
  Body: ```python
  from sktime.forecasting.arima import AutoARIMA
  ```
  cause UnicodeDecodeError as follwoing:
  
  '''
    File "C:\Users\lgzhangjian\scoop\apps\python310\3.10.11\lib\site-packages\sktime\base\_base.py", line 68
  , in <module>
      from sktime.utils._estimator_html_repr import _HTMLDocumentationLinkMixin
    File "C:\Users\lgzhangjian\scoop\apps\python310\3.10.11\lib\site-packages\sktime\utils\_estimator_html_r
  epr.py", line 190, in <module>
      _STYLE = style_file.read()
  UnicodeDecodeError: 'cp950' codec can't decode byte 0xe2 in position 4505: illegal multibyte sequence
  '''
  
  It is because "_estimator_html_repr.css" codec is 'utf8', 
  but "open" in  Windows 11 Traditional Chinese System with default codec 'cp950' as following:
  
  with open(Path(__file__).parent / "_estimator_html_repr.css") as style_file: # default codec with cp950 in windows 11 tranditional chinese
      # use the style defined in the css file
      _STYLE = style_file.read()
  
  it should open with specified codec with 'utf8'. 
  
  with open(Path(__file__).parent / "_estimator_html_repr.css", encoding='utf8') as style_file: chinese
      # use the style defined in the css file
      _STYLE = style_file.read()
  
  This fixes the problem.
  
  sktime versions:
  Name: sktime
  Version: 0.34.0
  