Fix the issue(#6022): Add additional installation method in README

[y-vectorfield]

Fit the issue #6022
Add additional installation method in README.

[matteius]

@y-vectorfield Can you explain more why this should be a preferred/supported installation method? I mean the change itself seems simple, but I wonder what is the difference between that and invoking pip directly?

[y-vectorfield]

Hello, @matteius, thank you very much for your comment.
Actually, we often cannot install pip command using package manager as sudors.
In addition, we often need to install python libraries into specific environment(~/.local).
This methdod(python -m pip ~) can install python libraries if we cannot install pip commad specific environment.
Hence, I think we should add this installation method.