Add how to compile doc.

examples/validator/README.md

@@ -9,6 +9,32 @@ Experimental. W.I.P.
 ## Requirements
 
 * C++11 compiler
+* CMake 3.2 or later
+
+## How to build
+
+```
+$ mkdir build
+$ cd build
+$ cmake ..
+$ make
+```
+
+## How to run
+
+First clone glTF repo somewhere to get glTF schema JSON files.
+
+```
+$ cd ~/work # Choose your favorite dir.
+$ git clone https://github.com/KhronosGroup/glTF
+$ export GLTF_DIR=~/work/glTF
+```
+
+Then, specify the directory of glTF 2.0 schema JSONs and a glTF file.
+
+```
+$ ./tinygltf-validator $GLTF_DIR/specification/2.0/schema/ ../../models/Cube/Cube.gltf
+```
 
 ## Third party licenses