Update docs for Dome

[anuj-tambwekar]

Master list for all the Dome-related docs

• update to use vijil-dome and remove all references to vijil-core
• update installation guide to point to the package branch
• add coming soon(s) if needed (for eg in adaptive dome)
• remove VijilOpenAI example
• remove guardgroup references and align with the cleanups
• add a quickstart/getting started
• make the flow easier on the reader. Start with a simple config and gradually work towards more complex ones. Same for TOML and dicts.
• breakdown the output info from a guardrail execution