fix(crypto): restore rendered example

[SoYuCry]

How I found this

I noticed that the Crypto section on the Metrics Embed GitHub Marketplace page did not display anything when expanding Render example.

Cause

The Crypto plugin metadata still referenced a via.placeholder.com placeholder instead of a generated example. That placeholder is no longer available. In addition, the Crypto example had prod.skip: true, so the examples workflow never generated metrics.plugin.crypto.svg on the examples branch.

Solution

• Enable the Crypto example in the production examples workflow by removing prod.skip.
• Point the Crypto preview metadata to metrics.plugin.crypto.svg on the examples branch, consistently with the other plugins.
• Keep the test example skipped so regular tests do not depend on the external CoinGecko API.

Once merged, the repository build workflow will regenerate the derived README and examples workflow files, and the examples workflow can publish the SVG used by the Marketplace preview.

Verification

• npm run build
• npm run test-contrib (26 tests passed)
• Confirmed the CoinGecko coin and market chart endpoints used by the plugin return HTTP 200.