Expand blocks definition in glossary with definitions of what precomputed and extensional blocks are.

[simisimis]

Recently I had to figure out what precomputed and extensional blocks were and what was the difference between them. Because this wasn't obvious to me or people I asked.

My suggestion would be to add terms Precomputed block and Extensional block to glossary, they both could point back to a Block definition, but expand on how are they different.

This is what I learned pulling together various internal and external sources:
Precomputed blocks are blocks logged by mina (daemon|application?) either to disk, log file or to google cloud storage.
Extensional blocks are blocks extracted from mina-archive database, compared to the precomputed blocks, are more lightweight as it only contains the information required to restore data to the archive node.