[Feature Request]: Create module gallery

### Feature description

As a new teal user
In order to navigate through the modules packages better
I would like to see a single list (index) with all the modules available

I oftentimes got a question about if and where is the list of all available modules. New people might find it difficult to navigate (and understand the differences) through `teal.modules.general`, `teal.modules.clinical` not to even mention `teal.osprey` or `teal.goshawk`.
I think that the `teal.gallery` is a perfect place to have it. Similarly to what we have for apps - we can have a gallery for individual modules.

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct.

### Contribution Guidelines

- [x] I agree to follow this project's Contribution Guidelines.

### Security Policy

- [x] I agree to follow this project's Security Policy.