Add totals to the Ready for Swift 6 charts

[daveverwer]

Thanks to @mattmassicotte for the feedback that led to this!

Adds new "total" marks that show the total number of packages when hovered.

They are associated with the various plots, so when you remove a plot the total also gets hidden.

Unchecking "Show totals" hides all totals.

This only affects the first chart, the total number of errors needs no totals.

[finestructure]

I was baffled for a moment why the total is 3396 and not ~7500 until I realised that we're constraining the list to recently updated packages. That's probably worth a note somewhere 🤔

[daveverwer]

I was baffled for a moment why the total is 3396 and not ~7500 until I realised that we're constraining the list to recently updated packages. That's probably worth a note somewhere 🤔

We have this:

[mattmassicotte]

Great stuff, thank you so much!

[mattmassicotte]

I have a potentially annoying question: why not just have a graph that goes down?

"number of packages with zero data race errors" "number of packges with data race errors"

I'd also possibly change this to:

"number of packges with Swift 6 errors"

But that's maybe being too pendant 😉

[daveverwer]

Has cheesy stock photography taught you nothing @mattmassicotte? Charts are best when they go up and to the right!

[mattmassicotte]

My understanding is this is only true in the nothern hemisphere...