[Bug Report] Dependency on full Rails is too broad

[Epigene]

Bit of a nit, but blanket dependency of Rails is throwing up security warnings like this one.

Any way to change that to something much smaller?
Looking at Rails' dependencies is's not immediately clear which are used by stimpack, most likely zeitwerk, but I'm not sure which of Rails' deps include it.

Maybe try:

s.add_dependency "activesupport"
s.add_dependency "railties"

[Epigene]

Sorry, was meant for stimpack rubyatscale/packs-rails#31