Switch to use nvidia-sphinx-theme

[leofang]

It's finally up on PyPI now: https://pypi.org/project/nvidia-sphinx-theme

[leofang]

I find it annoying that if we have past doc versions, all versions need to be rebuilt with the new theme... @szkarpinski I will have to peek how you did it for nvmath and other projects 😛

[szkarpinski]

all versions need to be rebuilt with the new theme...

@leofang do they? We didn't do it for DALI or nvmath. For example see the DALI docs - when you choose version <=1.38 in the switcher, you just get redirected to the docs in the old RTD theme.

[leofang]

Yes, but it's poor UX, because the different themes look up the version json files in different places, and the file format requirements are different too. For example, if you switch to DALI 1.38 version (the last version using the old RTD theme), there's no way to select any newer versions through the version drop-down menu (except for picking main, we might argue). If we're OK with this then it is indeed straightforward as you said.