Default to using colored emojis instead of badges for configs without emojis

[bmish]

After removing support for README-defined badges in #499, for any config without an explicit emoji/badge defined, we can just cycle through generic, colored circle/square emojis. These are easier for us to use anywhere we mention a config (in readme or rule doc) and require less setup from the user.

const emojis = [
  // circles
  '🔴',
  '🟠',
  '🟡',
  '🟢',
  '🔵',
  '🟣',
  '🟤',
  '⚫',
  '⚪',
  // squares
  '🟥',
  '🟧',
  '🟨',
  '🟩',
  '🟦',
  '🟪',
  '🟫',
  '⬛',
  '⬜',
];