message: fix warning for missing key prop
diff: @@ -74,7 +74,7 @@ const Index = props => (
  <Text>{`bg='${bg}'`}</Text>
  </td>
  {['white', 'gray', 'black'].map((fg, j) => (
  - <td>
  + <td key={j}>
  <Block p={3} mb={2} bg={bg}>
  <Text color={fg}>{fg}</Text>
  </Block>
  