Fix default encoding to UTF-8

[MrFox131]

Hello, @bitrate16 ! Were there any incidents because of lack of this parameter? It looks like really useless here for us. As I know, Windows have utf-8 by default in python, same about linux. Maybe it can be changed due to some territorial specifics? Let us know if so and we will accept this MR, until then it's not relevant for us.

[bitrate16]

@MrFox131, If I try to install this project with pip install ./ on win10 vscode integrated terminal (Powershell), it will crash with

  Preparing metadata (setup.py) ... error
  error: subprocess-exited-with-error

  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [10 lines of output]
      Traceback (most recent call last):
        File "<string>", line 2, in <module>
        File "<pip-setuptools-caller>", line 34, in <module>
        File "C:\Users\aboba\Documents\GitHub\image-background-remove-tool-4.0\setup.py", line 25, in <module>
          long_description=read('README.md'),
        File "C:\Users\aboba\Documents\GitHub\image-background-remove-tool-4.0\setup.py", line 16, in read
          return file.read()
        File "C:\Program Files\Python310\lib\encodings\cp1252.py", line 23, in decode
          return codecs.charmap_decode(input,self.errors,decoding_table)[0]
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.
note: This is an issue with the package mentioned above, not pip.
hint: See above for details.