Add tools layer doc

docs/layers/tools.md

@@ -0,0 +1,30 @@
+---
+title: "SpaceVim tools layer"
+description: "This layer provides some tools for vim"
+---
+
+# [SpaceVim Layers:](https://spacevim.org/layers) tools
+
+
+<!-- vim-markdown-toc GFM -->
+
+- [Description](#description)
+- [Install](#install)
+- [Commands](#commands)
+
+<!-- vim-markdown-toc -->
+
+## Description
+
+This layer provides some extra vim tools for SpaceVim. All tools can be
+called via command. no key bindings will be definded in this layer.
+
+## Install
+
+This layer is disabled by default in SpaceVim.
+
+To use this configuration layer, add `call SpaceVim#layers#load('tools')` to your custom configuration file.
+
+## Commands
+
+