Improve spec by including info on encoding and layer.json

For devs who want to create their own quantized mesh tiles, it would be helpful in the spec to have algorithms describing that process. It's great that there are very specific algorithms on the decoding process, but that makes the assumption that there is data already encoded. Some applications may need to create their own tile sets dynamically and serve them.

The encoding process has been the biggest hurdle for me, and I imagine others have faced similar issues.

Also, I've found various information scattered about regarding the layer.json file. Much more information on this file would be extremely helpful.

Start by reviewing the existing specification's decoding algorithms and the scattered information about layer.json. Identify what encoding guidance and layer.json details are missing, then document the relevant processes and verify that the specification addresses both needs.

Written by the indexing model from the issue text.