[Feature Request]: Create module gallery

[pawelru]

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.

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