message: Add comments to isRegionalIndicator
diff: @@ -35,8 +35,15 @@ export const EMOTICON_TO_EMOJI = new Map<string, IEmoji>();
  export const getEmojiFromUnicode = unicode => UNICODE_TO_EMOJI.get(stripVariation(unicode));
  -const isRegionalIndicator = (x: string): boolean =>
  - Array.from(x).length === 1 && x >= '\u{1f1e6}' && x <= '\u{1f1ff}';
  +const isRegionalIndicator = (x: string): boolean => {
  + // First verify that the string is a single character. We use Array.from
  + // to make sure we count by characters, not UTF-8 code units.
  + return Array.from(x).length === 1 &&
  + // Next verify that the character is within the code point range for
  + // regional indicators.
  + // http://unicode.org/charts/PDF/Unicode-6.0/U60-1F100.pdf
  + x >= '\u{1f1e6}' && x <= '\u{1f1ff}';
  +};
  const EMOJIBASE_GROUP_ID_TO_CATEGORY = [
  "people", // smileys
  