Update Argilla start page

[nataliaElv]

• Change link to docs from Rubrix to Argilla documentation
• Add a tab with a code snippet for Feedback datasets

[nataliaElv]

Code snippet for feedback datasets:

# install datasets library with pip install datasets
import argilla as rg
from datasets import load_dataset

# load an Argilla Feedback dataset from the Hugging Face hub
dataset = rg.FeedbackDataset.from_huggingface("argilla/oasst_response_quality", split="train")

# push the dataset to Argilla
dataset.push_to_argilla("oasst_response_quality")