Rework JuliaIntervals website

[OlivierHnt]

The purpose of this PR is to overhaul the current JuliaIntervals website which is completely outdated (with erroneous information).

I decided to use DocumenterVitepress.jl; I did little customization, but more can be done later on.

I think we should have a clean slate and close all current open issues. One of the main difference with the current website is that the version of this PR does not aim to provide tutorials and documentation of each package of the organisation.
This is too much work to maintain and update, so it makes more sense to only provide links to the docs of the corresponding package.

Closes #5; closes #6; closes #7; closes #8; closes #9; closes #11; closes #12; closes #13

Additional note: the tutorials (cf. https://juliaintervals.github.io/pages/tutorials/) should probably be migrated to the corresponding packages documentation. Also, maybe this webpage https://juliaintervals.github.io/pages/explanations/explanationNewton can be added to IntervalRootFinding.jl?
In any case, this can be done later and should not conflict with this PR.

cc @Kolaru, @lbenet, @lucaferranti, @dpsanders

[OlivierHnt]

You can see the generated webpage here: https://juliaintervals.github.io/previews/PR15/

[dpsanders]

Thanks so much for doing this, Olivier!
The new site looks great, but I only see the front page and don't see how to navigate to the rest of the docs.

[OlivierHnt]

Mhmm currently it is only a front page that provides links to the repository of the packages.

Maybe it is possible to incorporate the documentation of the packages automatically (without having to copy/duplicate the existing docs page from the repo of the packages).

[OlivierHnt]

Though I find it quite confusing to have two separate websites hosting the documentation, even if identical.

I thought JuliaIntervals website would be more of a front page pointing to the different packages in the ecosystem.

However, maybe you want the JuliaIntervals website to host the documentation of each package?

I suspect it will be too hard to maintain.
This is what ended up happening to the current JuliaIntervals website which is now completely out of sync...

For instance, we need to figure out a way to automatically deploy the JuliaIntervals website every time there is a new tagged version of one of the packages.

My current thinking is that we should at least have a correct website (here just a front page) (btw I used DocumenterVitepress because the default layout was kind of pretty and simple to configure, while I know nothing about Franklin...).
Migrating here the docs from the packages and stop deploying docs in each package repo could be a future direction if one wishes.

[Kolaru]

I think having direct link to the package documentation on the website is enough. In fact, I was expecting that the link would link to the doc rather than the github page.

[OlivierHnt]

Ah I see, yes maybe that is better.

[OlivierHnt]

IntervalOptimisation and IntervalConstraintProgramming do not have any documentation (there is only a tutorial on the JuliaIntervals website).
So for these two I kept the link to the repo.

[OlivierHnt]

Are there any objections to merging this PR?

[Kolaru]

Looks good to me.