What content needs to be in the description of species compendia Zenodo releases?

### Context

Related to #541, #981 -- came up in demo day yesterday. _Summarizing the discussion from demo day:_ We're planning to release species compendia via Zenodo, where they are uploaded by a CCDL user (
https://github.com/AlexsLemonade/refinebio/issues/981#issuecomment-455668570). Each species will have it's own concept/item. Initially, updates will be done manually.

### Problem or idea

Each Zenodo concept/item contains a description. This ticket is for keeping track of what we think should be included in that description.

What specifically came up in the meeting was how we should keep track of changes/a changelog in the description of _updates._

### Solution or next step

Tagging @Miserlou and @cgreene as they were the people discussing this.

### New Issue Checklist

- [x] The title is short and descriptive.
- [x] You have explained the context that led you to write this issue.
- [x] You have reported a problem or idea.
- [x] You have proposed a solution or next step.

Review this issue alongside #541 and #981, especially the linked #981 discussion about Zenodo uploads. Define and document the agreed content for each species compendium's Zenodo description, including how updates and changelogs should be represented; the work is done when the requirements have an explicit decision.

Written by the indexing model from the issue text.