docs(cli/verify): how to verify library contracts 🚗

[qbzzt]

Also:

1. Added how to get a Blockscout API key
2. Removed Etherscan references because it doesn't work

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: a60c4882771a9a927dfb941d99947f32ecb8d0f7

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