We call these "system images" and you can generate them with PackageCompiler [0]. Unfortunately, it's still a little cumbersome to create them, but this is something that we're improving from release to release. One possible future is where an environment can be "baked", such that when you start Julia pointing to that environment (via `--project`) it loads all the packages more or less instantaneously.
The downside is that generating system images can be quite slow, so we're still working on ways to generate them incrementally. In any case, if you're inspired to work on this kind of stuff, it's definitely something the entire community is interested in!
[0] https://github.com/JuliaLang/PackageCompiler.jl