Add "migrating" section for 0.9.3

Author: gaearon

CHANGELOG.md

@@ -41,6 +41,20 @@
 - Ryan Sullivan ([ryansully](https://github.com/ryansully))
 - Simon Vocella ([voxsim](https://github.com/voxsim))
 
+### Migrating from 0.9.2 to 0.9.3
+
+Inside any created project that has not been ejected, run:
+
+```
+npm install --save-dev --save-exact react-scripts@0.9.3
+```
+
+You may also optionally update the global command-line utility for offline Yarn cache support:
+
+```
+npm install -g create-react-app@1.2.0
+```
+
 ## 0.9.2 (February 26, 2017)
 
 #### :nail_care: Enhancement