fix(#43): Load all schemas before validating them

[iainjreid]

Hello! This PR ensures that all of the schemas passed through the CLI are loaded before they're validated, allowing schemas to cross reference each other without having to be loaded in a given order 👍

[iainjreid]

~~I should add that the install fails for me locally, I'm not sure if this is because the lock file is missing, and the dependencies have moved on since the CI was last ran?~~

I've locked the version of TypeScript in the package file to prevent the build failures 👍