fix: downgrade @babel/preset-env temporarily

[haoqunjiang]

seems there're still problems with it, e.g. when core-js 3 is hoisted as the root level dependency.

[jacekkarczmarczyk]

@sodatea Can you describe the problem? I'm not sure if it doesn't affect my app or I just don't see it

[haoqunjiang]

@jacekkarczmarczyk @babel/preset-env 7.4+ introduced an indirect dependency of core-js@3, in some cases, core-js@3 is incorrectly hoisted to node_modules root. Meanwhile, @babel/preset-env injects code like import "core-js/...", which expects core-js 2 directory structure, that will cause problem.

I'm not sure how it happened as I personally didn't encounter this problem, but I guess it may happen when you use transpileDependencies.

To ultimately solve this problem we may need to add core-js@2 as direct dependency to the generated projects.