A runtime service to extract avatar images from:

1. <link rel="apple-touch-icon">
2. <link rel="apple-touch-icon-precomposed">
3. <link rel="icon">
4. favicon.ico (added September 20, 2021)
5. TODO: Support Data URIs in attribute values. (e.g. https://joshcrain.io)
6. TODO: <link rel="mask-icon">
7. TODO (maybe): <link rel="manifest">
8. TODO (maybe): <meta name="msapplication-config">

All rel lookups match against attribute values that are space separated lists.

URLs have the formats:

/:url/

• url must be URI encoded.