Feature Request: Add current file to Cabal (exposed/other) modules

**Is your feature request related to a problem? Please describe.**

Adding all project modules to the Cabal file is often confusing for newcomers, if we could add them automatically, it'd be a win.

**Describe the solution you'd like**

When a module in the project is opened and it is not mentioned in the Cabal file, it should be added automatically to the `other-modules` section.

This would be a quick boost of productivity, so the developer would only need to move the module to `exposed-modules` if they want to expose it.

An alternative would be to add a command to the extension to achieve this on demand.

**Describe alternatives you've considered**

Using/creating a CLI file just for this

**Additional context**

In F# Ionide this is done through an additional file explorer view, which is overkill in my opinion. Still, it frees the dev from having to mess around with tooling.