Update emoji list in Text.Pandoc.Emoji.

Done using tools/emojis.hs, which uses the list from the
gem GitHub uses.  Future updates can be done with this tool.

Closes #5666.

tools/emojis.hs

@@ -0,0 +1,36 @@
+-- Script to generate the list of emojis in T.P.Emoji.hs.
+-- to run:
+-- curl https://raw.githubusercontent.com/github/gemoji/master/db/emoji.json -o emoji.json
+-- stack script --resolver lts-13.17 --package aeson --package bytestring --package text --package containers tools/emojis.hs < emoji.json
+
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE OverloadedStrings #-}
+import Data.Aeson
+import qualified Data.ByteString.Lazy as B
+import Data.Text (Text)
+import Data.Map as M
+
+data Emoji = Emoji Text [Text]
+  deriving Show
+
+instance FromJSON Emoji where
+    parseJSON = withObject "Emoji" $ \v -> Emoji
+        <$> v .: "emoji"
+        <*> v .: "aliases"
+
+main :: IO ()
+main = do
+  bs <- B.getContents
+  case eitherDecode bs of
+    Left e -> error e
+    Right (emoji :: [Emoji]) -> do
+      let emojis = M.fromList $
+           [(alias, txt) | Emoji txt aliases <- emoji, alias <- aliases]
+      putStrLn $ prettify $ dropWhile (/='[') $ show emojis
+
+prettify :: String -> String
+prettify [] = ""
+prettify ('[':xs) = '\n':' ':' ':'[':prettify xs
+prettify (']':xs) = '\n':' ':' ':']':prettify xs
+prettify (',':'(':xs) = '\n':' ':' ':',':'(':prettify xs
+prettify (x:xs) = x:prettify xs