Move Psiagram to peer dependency for plugins

[liamross]

Problem

1. Psiagram is technically a peer dependency rather than a direct dependency of the packages, since they must be used in conjunction with Psiagram
2. Bundle size is being inaccurately displayed as it accounts for Psiagram in the bundle size

Solution

1. Move Psiagram to peer dependency

Alternatives

1. Don't move it, but this doesn't solve any of the problems.

Additional context