[R-234] docs: update and fix documentation

[mancaldel]

Some of the pages in the documentation are out of date or incorrect and it make it difficult to have a general idea about the capabilities of the library. Here are a few examples:

• References/Metrics: the summary at the beginning does not include all implemented metrics, missing 4/10 (AspectCritique, ContextRelevancy, ContextUtilization, Faithfulness). Also, there is no info about the definition of the last metrics in the list.
• Concepts/metrics: also missing some metrics, 2/10 in the page (AspectCritique, ContextUtilization), and 1/10 in the side bar (ContextUtilization)
• Integrations: friendly reminder that the page is empty.

Thanks!

_R-234

[jjmachan]

Hey @mancaldel

thank you for keeping us honest - will be updating these shortly Manuel 🙂