Need support spree_core > 4

[RubyDiver]

Bundler could not find compatible versions for gem "spree_core":
In snapshot (Gemfile.lock):
spree_core (= 4.3.0)

spree_easypost was resolved to 1.1.0.alpha, which depends on
spree_core (>= 3.1.0, < 4.0)

It is impossible to install spree_easypost with spree_core> 4.0 which I think has a lot of developers.