feat(sml): add treesit (and lsp) support

modules/lang/sml/README.org

@@ -4,17 +4,23 @@
 #+since:    21.12.0
 
 * Description :unfold:
-THis module adds [[https://smlfamily.github.io/][SML (Standard ML) programming language]] support to Doom Emacs.
+This module adds [[https://smlfamily.github.io/][SML (Standard ML) programming language]] support to Doom Emacs.
 
 ** Maintainers
 *This module needs a maintainer.* [[doom-contrib-maintainer:][Become a maintainer?]]
 
 ** Module flags
-/This module has no flags./
+- +lsp ::
+  Enable LSP support for ~sml-mode~/~sml-ts-mode~. Requires [[doom-module::tools lsp]]
+  and a langserver (supports [[https://github.com/azdavis/millet][millet-ls]]).
+- +tree-sitter ::
+  Leverages tree-sitter for better syntax highlighting and structural text
+  editing. Requires [[doom-module::tools tree-sitter]].
 
 ** Packages
 - [[doom-package:company-mlton]] if [[doom-module::completion company]]
 - [[doom-package:sml-mode]]
+- [[doom-package:sml-ts-mode]] if [[doom-module:+tree-sitter]]
 
 ** Hacks
 /No hacks documented for this module./