Add lang/sml module

Closes #1947

modules/lang/sml/README.org

@@ -0,0 +1,39 @@
+#+TITLE:   lang/sml
+#+DATE:    March 29, 2020
+#+SINCE:   v3.0
+#+STARTUP: inlineimages nofold
+
+* Table of Contents :TOC_3:noexport:
+- [[#description][Description]]
+  - [[#maintainers][Maintainers]]
+  - [[#module-flags][Module Flags]]
+  - [[#plugins][Plugins]]
+- [[#prerequisites][Prerequisites]]
+- [[#features][Features]]
+- [[#configuration][Configuration]]
+- [[#troubleshooting][Troubleshooting]]
+
+* Description
+This module has no description yet.
+
+** Maintainers
+This module has no dedicated maintainers.
+
+** Module Flags
+This module provides no flags.
+
+** Plugins
++ sml-mode
++ company-mlton (=:completion company=)
+
+* TODO Prerequisites
+# Document how to install sml program and MLton
+
+* TODO Features
+# An in-depth list of features, how to use them, and their dependencies.
+
+* TODO Configuration
+# How to configure this module, including common problems and how to address them.
+
+* TODO Troubleshooting
+# Common issues and their solution, or places to look for help.