Update haskell layer doc

docs/layers/lang/haskell.md

@@ -10,12 +10,19 @@ description: "Haskell language support for SpaceVim, includes code completion, s
 - [Description](#description)
 - [Install](#install)
 - [Features](#features)
+- [Key bindings](#key-bindings)
+  - [Running current script](#running-current-script)
+  - [Inferior REPL process](#inferior-repl-process)
 
 <!-- vim-markdown-toc -->
 
 ## Description
 
-This layer is for Haskell development.
+This layer is for Haskell development. This layer includes following plugins:
+
+- haskell.vim: syntax highlight and indent
+- vim-syntax-shakespeare: syntax files for the shakespeare templating languages
+- neco-ghc: completion plugin for Haskell
 
 ## Install
 
@@ -26,11 +33,31 @@ To use this configuration layer, update custom configuration file with:
   name = "lang#haskell"
 ```
 
+After updating configuration file, restart SpaceVim and run `:SPInstall`.
+
 ## Features
 
-- auto-completion
+- code completion
 - syntax checking
 - goto definition
 - refernce finder
 - language server protocol (need lsp layer)
 
+## Key bindings
+
+### Running current script
+
+To running a haskell file, you can press `SPC l r` to run current file
+without loss focus, and the result will be shown in a runner buffer.
+
+### Inferior REPL process
+
+Start a `ghci` inferior REPL process with `SPC l s i`.
+
+Send code to inferior process commands:
+
+| Key Bindings | Descriptions                                     |
+| ------------ | ------------------------------------------------ |
+| `SPC l s b`  | send buffer and keep code buffer focused         |
+| `SPC l s l`  | send line and keep code buffer focused           |
+| `SPC l s s`  | send selection text and keep code buffer focused |