`chunk_key_encoding` description does not link to actual chunk key encoding definitions

[d-v-b]

The chunk_key_encoding definition does not link to the list of core chunk key encoding definitions. We should add that link.

[joshmoore]

Hmmm .... looks like this is true for all of the extensions. They point to the extension table which then links to the individual lists.

[d-v-b]

The same principle applies to the other extensible fields -- the codecs field should link to the list of codecs. Should I update the issue, or should I assume that we can add all of the missing links in one PR?

[joshmoore]

I'd certainly prefer a PR with all of them. 👍 I was going to just add to #362 but then realized that it needed more cross-checking / linking so held off.