porting the prelude

Stream: mathlib4

[Ruben Van de Velde]

Do we have an easy way of tracking which files from the lean 3 core prelude have not been ported? I occasionally run into some of the more obscure lemmas there being missing (e.g. !4#4281), but it'd be interesting to have a better view of the situation

[Mario Carneiro]

if we had an easy way to mark files as skipped, we should just be able to add them to the port dashboard

[Mario Carneiro]

the whole infrastructure is set up for them, in the lean3port directory instead of mathlib3port, it's just the port-progress bot and leanproject port-progress that ignore init files