feat(format): add :lang crystal formatter

modules/lang/crystal/config.el

@@ -1,6 +1,9 @@
 ;;; lang/crystal/config.el -*- lexical-binding: t; -*-
 
 (after! crystal-mode
+  (when (executable-find "crystal")
+    (set-formatter! 'crystal-mode '("crystal" "tool" "format" "-") :modes '(crystal-mode)))
+
   (set-lookup-handlers! 'crystal-mode
     :definition #'crystal-def-jump
     :references #'crystal-tool-imp)

modules/lang/crystal/doctor.el

@@ -3,3 +3,6 @@
 
 (unless (executable-find "icr")
   (warn! "Couldn't find icr. REPL will not work"))
+
+(unless (executable-find "crystal")
+  (error! "Couldn't find crystal. Most language features will not work."))