Adding the gcc, gxx, pybind to the env file. Preparing for packaging

[DomInvivo]

Changelogs

• Changing the env.yml file to contain all the gcc requirements
• Updating the install instructions

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Issues to resolve:

• [ ] Currently only supports linux x64 because the gcc and gxx do not work in the env file, we need to specify gcc_linux-64 and gxx_linux-64. Ideally, we want to support Win64, WinARM, Linux64, LinuxARM, Mac64, MacARM
• [ ] Weirdly, gcc --version and gxx --version don't appear in the command line. We need to rename their folders ln -s MY_ENV_PATH/bin/x86_64-conda-linux-gnu-gcc MY_ENV_PATH/bin/gcc, same with gxx.
• [ ] When in dev mode, we need to build graphium/graphium_cpp separately with pybind11, then install it with pip install -e graphium_cpp --no-deps. Ideally, all should be built and installed from directly pip install -e . --no-deps.