Previously, in #2 I suggested to allow passing a number of CLI arguments, which isn't very nice from the UX standpoint, but it meant to accomplish a single goal — to allow copy-pasting a pre-made project creation command and starting right away.

This goal is invaluable for the docs and as a quick onboarding step, so here's a different solution: we could allow a presence of a single CLI argument that can be called --quickstart, --onboarding, --cookbook, --showcase or somesuch, and it will attempt to always create a tact-quickstart folder with the special, documentation-packed template contents that will be discussed on the front page of Tact docs.

Needed for: tact-lang/tact#2872