sync downstream projects to `v2.8`of `vocabulary-theme`

## Description
`vocabulary-theme` received changes:
* #175
* #176
* #177
* #178
* #179
* #181
* #182
* #183
* #184
* #187
* #188
* #189
* #190
* #191
* #192
* #193

`vocabulary-theme` needs to be updated to `v2.9` in the following projects:
* `index-dev-env`
- https://github.com/creativecommons/index-dev-env/pull/129
- deploy to `index__stage`
- `v2.9` ✅
- deploy to `index__prod`
- `v2.9` ✅

* 👉 `cc-legal-tools-*` _(includes changes to `vocabulary`, legal-tools adjacent markup should be unchanged)_
- https://github.com/creativecommons/cc-legal-tools-app/issues/576
- cc-legal-tools-app PR tbd
- cc-legal-tools-data PR tbd

# Technical Details

supersceded versions:

- `v2.6.2`
- `v2.6.3`
- `v2.7`
- `v2.7.1`
- `v2.8`

This version makes changes to the entire codebase, template files, and core vocabulary.

## Implementation

- [x] I would be interested in implementing this feature.