Update installation guide to briefly mention that blobs will bloat the requirements

[matthewdarwin]

The docs here https://lighthouse-book.sigmaprime.io/installation.html are quite old and don't address blob storage.

There is a detailed document about blobs here: https://lighthouse-book.sigmaprime.io/advanced_blobs.html

Request:

• update installation guide to mention that blob storage (depending on options selected) may require a very fast CPU (5Ghz) and TiBs of storage space (for supernode archive blobs as example)