README: new doc: Add links for 4th level sections

README.md

@@ -7,13 +7,28 @@ Ultralightweight JSON parser in ANSI C.
 * [Usage](#usage)
   * [Welcome to cJSON](#welcome-to-cjson)
   * [Building](#building)
+    * [Copying the source](#copying-the-source)
+    * [CMake](#cmake)
+    * [Makefile](#makefile)
   * [Including cJSON](#including-cjson)
   * [Data Structure](#data-structure)
   * [Working with the data structure](#working-with-the-data-structure)
+    * [Basic types](#basic-types)
+    * [Arrays](#arrays)
+    * [Objects](#objects)
   * [Parsing JSON](#parsing-json)
   * [Printing JSON](#printing-json)
   * [Example](#example)
+    * [Printing](#printing)
+    * [Parsing](#parsing)
   * [Caveats](#caveats)
+    * [Zero Character](#zero-character)
+    * [Character Encoding](#character-encoding)
+    * [C Standard](#c-standard)
+    * [Floating Point Numbers](#floating-point-numbers)
+    * [Deep Nesting Of Arrays And Objects](#deep-nesting-of-arrays-and-objects)
+    * [Thread Safety](#thread-safety)
+    * [Case Sensitivity](#case-sensitivity)
   * [Enjoy cJSON!](#enjoy-cjson)
 
 ## License