[feature] Update Documentation

[AnthonyCamper]

Documentation Suggestions:

• Explain "Tavern" as a term under https://docs.realm.pub/user-guide/terminology
• Activating User examples should be under its own header of "Adding Users", on https://docs.realm.pub/admin-guide/tavern
• Add/mention devcontainer setup documentation then link it under imix build guide (https://rustup.rs/) (https://docs.realm.pub/user-guide/imix)

[hulto]

Thanks @AnthonyCamper While were doing docs fixes i'd like to add: make it more clear that reflective loader is always required

This should be a simple update to https://docs.realm.pub/user-guide/imix#windows

Adding a text blurb just under the windows header saying:

_Building the reflective loader is always required to build imix do not skip it will cause your builds to fail._

[hulto]

We probably don't want to break Activating users out into its own section since long term it should be a UI flow.