Add `asyncData` return types to component instance type

Editor assessment

The subject states precisely what was added and where it surfaces — `asyncData` return types on the component instance type — so the header communicates the improvement without the diff, and feat(types) classifies and locates it correctly. Hygiene is clean throughout: imperative mood, no trailing period, reasonable length, no ticket junk. No body is present, which is tolerable for a typing addition, though a line about the ergonomics gap it closes would have helped. No footer is required since nothing breaks. Clear, accurate, and publishable: a good example.