Add app explorer

[Velua]

App	UI	Service	Plugin
Registry	No	Yes	Yes
Workshop	Yes	No	No
Apps	Yes	No	No

App Registry

This is an unopinonated service, used chain-wide across all chains,

Workshop

An all round developer centric application used to register apps, but also maintain them over their life time, developers should be able to do everything they need to here.

Apps (app explorer)

Read only app, used to explore deployed apps on the app registry, render whatever metadata it can just like an app store.

[swatanabe]

The name Explorer is already taken.

[James-Mart]

Rewording the title of this to make it about the apps explorer because the registry was already delivered, and theres already at least one other issue related to workshop https://github.com/gofractally/psibase/issues/77