feat: add modules option to allow flakeModules to add options to every devshell

[TECHNOFAB11]

This PR adds an option devenv.modules which takes an array of module types (paths, functions and attrsets) and forwards them into all shells.

That makes it way easier for flake modules (when using flake-parts) to add custom options for shells.
For example, it would allow my nix-devtools to easily add task and teller integration without the user having to add imports into every shell. (see feat/flakeModule for example)