Castopod favicon fingerprint

Description

Add a fingerprint for Castopod based entirely on the favicon

Notes

<link rel="icon" type="image/x-icon" href="/favicon.ico" />

This was pulled from the current-latest of Castopod, version 1.0.2.

Alas, there were no interesting cookies or <title> tags to sample -- Castopod is built using CodeIgniter and just uses a ci_session session cookie without renaming, and <title> tags are entirely custom to the content being hosted.

Motivation and Context

After Twitter changed ownership October of 2022, Fediverse services kind of exploded all over the internet. It would be nice to track them. I suspect there are a lot of new server operators who are diving into the deep end of self-hosted services.

How Has This Been Tested?

Collected the MD5 of the favicon, hoping for the best! I need to figure out how to test locally.

Types of changes

New feature (non-breaking change which adds functionality)

Checklist:

[x] I have updated the documentation accordingly (or changes are not required).
[x] I have added tests to cover my changes (or new tests are not required).
[x] All new and existing tests passed.

rapid7 / recog