Link to Vocabulary from the Downloads page

## Problem
The downloads page provides icons and badges for use in different media. [CC Vocabulary](https://cc-vocabulary.netlify.app) is a convenient way to include these icons on the web so it should be linked to from that particular page.

## Description
Linking to Vocabulary would give developers the information that Vocabulary is an easier alternative to embed these icons as vector graphics on webpages.

## Alternatives
Downloading SVG assets and using them on websites (the current solution) is perfectly valid and viable but it is a little complex. Using Vocabulary is easier as it provides a web font for easier embeds.

## Implementation

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

Start at the Downloads page and identify where links to web resources are presented. Add a link to CC Vocabulary with enough context to explain that it simplifies embedding the icons as web graphics; done means the link is visible and accurately describes this benefit.

Written by the indexing model from the issue text.