Add process class for managing external processes

[DalisonCPU]

This pull request introduces the process class, which allows launching and managing external processes with input/output stream support.
It includes:
•
Implementation of the process class
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Encoding conversion support for Windows (OEM and ACP modes)
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Basic documentation for usage
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A test for the process class
Notes
The class is cross-platform and should work on Linux and macOS, but it has only been tested on Windows so far.
Some features like encoding conversion are Windows-specific.

[DalisonCPU]

@samtupy I tried to correct the datastream by blocking the main script. I would like you to look like it is now. Tell me what has to be done and I'm updating here.
The code still has things from the previous code, so I will still have to remove them