fix: add proper encoding parsing for when working with Windows files

[Rewaster]

On Windows 10, when trying to use tbump to push tags in my environment, I was getting the following error:

Error code snippet

(my-test-project) PS C:\Users\Dan\PycharmProjects\my-test-project> tbump 0.0.1.dev10
:: Bumping from 0.0.1.dev9 to 0.0.1.dev10
Traceback (most recent call last):
File "", line 198, in _run_module_as_main
File "", line 88, in run_code
File "C:\Users\Dan\PycharmProjects\my-test-project.venv\Scripts\tbump.exe_main.py", line 10, in
sys.exit(main())
~~~~^^
File "C:\Users\Dan\PycharmProjects\my-test-project.venv\Lib\site-packages\tbump\cli.py", line 296, in main
run(args)
~~~^^^^^^
File "C:\Users\Dan\PycharmProjects\my-test-project.venv\Lib\site-packages\tbump\cli.py", line 184, in run
run_bump(arguments, working_path, arguments.tag_message)
~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\Dan\PycharmProjects\my-test-project.venv\Lib\site-packages\tbump\cli.py", line 208, in run_bump
bump(bump_options, _construct_operations(arguments))
~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\Dan\PycharmProjects\my-test-project.venv\Lib\site-packages\tbump\cli.py", line 250, in bump
executor = Executor(new_version, file_bumper, config_file)
File "C:\Users\Dan\PycharmProjects\my-test-project.venv\Lib\site-packages\tbump\executor.py", line 64, in init
file_bumper.get_patches(new_version),
~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
File "C:\Users\Dan\PycharmProjects\my-test-project.venv\Lib\site-packages\tbump\file_bumper.py", line 187, in get_patches
patches_for_request = self.compute_patches_for_change_request(
change_request
)
File "C:\Users\Dan\PycharmProjects\my-test-project.venv\Lib\site-packages\tbump\file_bumper.py", line 205, in compute_patches_for_change_request
old_lines = file_path.read_text().splitlines(keepends=False)
~~~~~~~~~~~~~~~~~~~^^
File "C:\Users\Dan\AppData\Roaming\uv\python\cpython-3.13.3-windows-x86_64-none\Lib\pathlib_local.py", line 546, in read_text
return PathBase.read_text(self, encoding, errors, newline)
~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\Dan\AppData\Roaming\uv\python\cpython-3.13.3-windows-x86_64-none\Lib\pathlib_abc.py", line 633, in read_text
return f.read()
~~~~~~^^
File "C:\Users\Dan\AppData\Roaming\uv\python\cpython-3.13.3-windows-x86_64-none\Lib\encodings\cp1251.py", line 23, in decode
return codecs.charmap_decode(input,self.errors,decoding_table)[0]
~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
UnicodeDecodeError: 'charmap' codec can't decode byte 0x98 in position 4611: character maps to

The same project works fine in Linux. Since it was pointing to the pathlib's read_text, which allows for explicit encoding setup, I tried to set the encoding explicitly, which allowed tbump to work without issue. Haven't tested this thoroughly, but this doesn't seem like too much of a change. Would be glad to fix anything else related to this if required.