Add :ui pretty-code & set-pretty-symbols! autodef

Along with defaults for C/C++, elm, elisp, js, typescript, web-mode, and
org-mode. Thanks to @ar1a for inspiration.

modules/lang/elm/config.el

@@ -6,7 +6,16 @@
 (after! elm-mode
   (add-hook 'elm-mode-hook #'rainbow-delimiters-mode)
   (set-company-backend! 'elm-mode 'company-elm)
-  (set-repl-handler! 'elm-mode #'run-elm-interactive))
+  (set-repl-handler! 'elm-mode #'run-elm-interactive)
+  (set-pretty-symbols! 'elm-mode
+    :null "null"
+    :true "true" :false "false"
+    :int "Int" :str "String"
+    :float "Float"
+    :bool "Bool"
+
+    :not "not"
+    :and "&&" :or "||"))
 
 
 (def-package! flycheck-elm