Add identifiers for different log types

[RangerMauve]

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Right now the CLI output of rn-tape is pretty noisy. There's TAP style output from the tests, error logging, and output from npm install and the react-native CLI.

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It could be useful to add some extra content to the logs so that users could differentiate between different types of logs, e.g. prefixing error lines with e and extra messages with s.

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Might be useful to hide these logs by default or to put them behind flags.

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