entity service seems to be missing

[Alexnortung]

I am currently developing a plugin that should fetch things using strapi's entityservice.

With strapi's own Strapi type, I do have access to the entityservice, but not when using strapi-typed's IStrapi. It should at least be there as an any type.

[boazpoolman]

Also +1 for this feature. If any of the maintainers can approve on this I could set up a PR.