Docs, samples & pkg. seem to be ought of sync.

``` go
gitpod /workspace/log/examples/styles ((f36448c...)) $ go mod tidy
gitpod /workspace/log/examples/styles ((f36448c...)) $ go run .
# examples/styles
./styles.go:12:6: undefined: log.ErrorLevelStyle
./styles.go:20:6: undefined: log.KeyStyles
./styles.go:21:6: undefined: log.ValueStyles
```