Update installation instructions

[PabloAndresCQ]

Long overdue improvement of installation experience.

I'd like to make a release once this is merged (so that installation from pypi pulls cuquantum-python), so I've bumped the version.

[PabloAndresCQ]

The build test without GPU in CI is failing due to me including cuquantum-python in the dependencies, which fails when cuda-toolkit is not available. However, it works fine in the CI with GPU.

@jake-arkinstall I suggest we kill the CI checks that build pytket-cutensornet on non-GPU CI. Agreed? We'd need to do the lint check in the nix CI (I believe it's not done atm?)

[jake-arkinstall]

Yes, having it all run in a cuda environment makes sense. I'll take a look at linting.

[PabloAndresCQ]

Actually, now that I think about it, the linting passes can be run on a machine without cuda (I used to do that when I developed on my work laptop), so the linter can stay in the standard CI. Looks like the error has nothing to do with the builder.

I'll update CI myself and mark it as ready for review when I'm done (I'll probably do it tomorrow). Thanks Jake!