Add charon examples to blockprint to identify charon blocks

[OisinKyne]

Problem to be solved

We want to better introspect the number of validators running charon. One of the low trust ways to approximate it, is to measure the number of charon blocks produced.

Proposed solution

Blockprint

This repo is an ml classifier of blocks. This PR might give us an indication about how we go about classifying us as existing client. Or we might have to add training data as described here, sigp/blockprint#1 (we would also need to have blocks produced with charon in that training data, the data that's in the repo if for mainnet won't include any charon blocks)

Relevant from Arisk

Out of Scope

If there is anything to highlight as out of scope for this issue, please outline it here.