Warn about sharing of secrets

[conorsch]

The bot is designed to disburse funds to any valid penumbra wallet address, currently prefixed with penumbrav2t. Folks new to the platform may mistakenly share secrets, such as a full viewing key. Let's consider warning those folks about the need to rotate those secrets if shared in the bot channel. For reference, see the list of BECH32_PREFIX values in https://github.com/penumbra-zone/penumbra/blob/main/proto/src/serializers/bech32str.rs#L168