Update 'README.md'

README.md

@@ -1,2 +1,27 @@
 # fvm
 
+安装管理多个flutter环境
+
+https://git.yoqi.me/flutter/fvm/_edit/master/README.md
+
+
+
+## Usage
+
+```
+# 安装
+dart pub global activate fvm
+
+# 列出所有环境
+fvm list
+
+fvm install 2.0.3
+
+fvm use 2.0.3
+
+fvm remove 2.0.3
+
+```
+
+
+