updates readme

Author: d3cod3

README.md

@@ -127,6 +127,7 @@ git clone https://github.com/d3cod3/ofxFFmpegRecorder
 git clone https://github.com/d3cod3/ofxFontStash
 git clone https://github.com/d3cod3/ofxGLEditor
 git clone https://github.com/jeffcrouse/ofxJSON
+git clone https://github.com/d3cod3/ofxImGui
 git clone https://github.com/d3cod3/ofxInfiniteCanvas
 git clone --branch=of-0.10.0 https://github.com/d3cod3/ofxLua
 git clone https://github.com/d3cod3/ofxMidi