Add migration instruction for 2.13.0

Author: DorianGrey

README.md

@@ -21,6 +21,20 @@ npm start
 
 In general, most upgrades won't require any migration steps to work, but if you experience problems after an upgrade, please file an issue, and we'll add it to the list of migration steps below.
 
+### From `<2.13.0` to `>=2.13.0`
+
+Since `2.13.0`, `typescript` is listed as a peer dependency of `react-scripts-ts`. For projects generated with at least this version, the init script takes care of properly installing it as dev dependency to the generated projects. Older projects require manual installation, in case you have not already done that.
+
+Using `npm`:
+```
+npm i -D typescript
+```
+
+Using `yarn`:
+```
+yarn add -D typescript
+```
+
 ### From `<2.5.0` to `>=2.5.0`
 
 Version `2.5.0` introduces a new config file for jest, that is necessary for the tests to run. If you were previously running a version older than `v2.5.0` and upgraded to `v2.5.0` or newer, you need to manually add the new file, or else you'll get an error similar to this when trying to run your tests: