Update 'README.md'

README.md

@@ -1,2 +1,22 @@
 # jan
 
+
+## Usage
+
+支持windows，linux，mac，Android等多平台
+
+源码构建：
+```
+git clone https://github.com/janhq/jan
+git checkout DESIRED_BRANCH
+cd jan
+
+yarn
+yarn build:core
+yarn build:plugins
+yarn build:uikit
+
+yarn dev
+yarn build
+
+```