Add waterfall chart example

[yanghung]

[joelostblom]

@yanghung When you are addressing the comments I made, could you also rebase this on the latest main branch so that the CI tests above pass (I recently committed a fix)?

[binste]

If you merge the PR in its current state I can create a follow-up one in the next few days to address the open points. If it doesn't work due to the failed checks I can also copy over the code from here and add @yanghung as an author.

[mattijn]

Thanks @binste! Which category is this supposed to be? It's currently in other charts but that category is not there anymore.

[binste]

As it contains quite a few transformations I'd suggest to place it into Advanced Calculations # category: advanced calculations.

[mattijn]

thanks again @yanghung, and the floor is yours @binste;)