Add lang/sml module

Closes #1947

modules/lang/sml/config.el

@@ -0,0 +1,27 @@
+;;; lang/sml/config.el -*- lexical-binding: t; -*-
+
+(use-package! sml-mode
+  :mode "\\.s\\(?:ml\\|ig\\)\\'"
+  :config
+  (set-repl-handler! 'sml-mode #'run-sml)
+
+  ;; don't auto-close apostrophes (type 'a = foo) and backticks (`Foo)
+  (sp-with-modes 'sml-mode
+    (sp-local-pair "'" nil :actions nil)
+    (sp-local-pair "`" nil :actions nil))
+
+  (map! :map sml-mode-map
+        :i "RET"   #'reindent-then-newline-and-indent
+        :i "M-SPC" #'sml-electric-space
+        :i "|"     #'sml-electric-pipe
+        :localleader
+        :desc "Run SML" "'" #'run-sml
+        :prefix ("e" . "eval")
+        :desc "Run buffer"                  "b" #'sml-prog-proc-send-buffer
+        :desc "Run the paragraph"           "f" #'sml-send-function
+        :desc "Run region"                  "r" #'sml-prog-proc-send-region))
+
+
+(use-package! company-mlton
+  :when (featurep! :completion company)
+  :hook (sml-mode . company-mlton-init))