add TOC to Semantic layer

layers/semantic/README.org

@@ -1,8 +1,13 @@
 #+TITLE: Semantic layer
 #+HTML_HEAD_EXTRA: <link rel="stylesheet" type="text/css" href="../../css/readtheorg.css" />
 
-* Description
+* Table of Contents                                         :TOC_4_org:noexport:
+ - [[Description][Description]]
+ - [[Features][Features]]
+ - [[Install][Install]]
+ - [[Key Bindings][Key Bindings]]
 
+* Description
 CEDET is a *C*ollection of *E*macs *D*evelopment *E*nvironment *T*ools written
 with the end goal of creating an advanced development environment in Emacs.
 CEDET includes common features such as intelligent completion, source code
@@ -18,7 +23,6 @@ perform smart code refactoring that based on code structure of the analyzed
 language, instead of plain text structure. Semantic is the core of CEDET.
 
 * Features
-
 - Display function or variable definition at the bottom.
 - Display current function cursor is in at the top. See
   [[https://github.com/tuhdo/semantic-stickyfunc-enhance][this page]] for demos in some programming languages.
@@ -37,4 +41,4 @@ file.
 
 | Key Binding | Description                         |
 |-------------+-------------------------------------|
-| ~SPC m r~   | srefactor: refactor thing at point. |
+| ~SPC m r~   | srefactor: refactor thing at point. |