update readme

README.md

@@ -1,6 +1,8 @@
 # justmd
 Simple markdown editor based on electron.
 
+![](http://www.i38.me/public/images/sync-scroll.gif)
+
 # run
 npm install
 npm start
@@ -10,15 +12,21 @@ before build:
 set ELECTRON_MIRROR=http://npm.taobao.org/mirrors/electron/
 
 for windows package:
+```
 npm run package-x86
+```
 or
+```
 npm run package-x64
+```
 
 for osx package(must use osx host):  
+```
 npm run package-osx
+```
 
 ## todo
-osx paste html
-splitter
-sequence https://bramp.github.io/js-sequence-diagrams/
-flow http://flowchart.js.org/ 
+* osx paste html
+* splitter
+* sequence https://bramp.github.io/js-sequence-diagrams/
+* flow http://flowchart.js.org/