Add NAIP example notebook

[kylebarron]

Change list

• Example NAIP notebook that downloads 1000 items from the planetary computer and converts to Arrow, Delta Lake, Parquet
• Added notebook to docs site
• Added download button to docs site to download notebook
• Added warning banner if not viewing the latest version of the docs

[TomAugspurger]

We can simplify this slightly by not using planetary_computer.sign. That injects a short-lived SAS token into the asset HREFs that probably isn't proper to store.

I confirmed that the rest of the notebook still works fine, since sign is only needed to read assets, and this notebook only uses metadata (I'll want to update planetary_computer.sign to also work on pyarrow Tables containing stac-geoparquet, but that's separate).

[kylebarron]

I removed signing from the notebook