[docs] howto turn off watch mode

Taken from here: jaredpalmer#319 (comment)

README.md

@@ -450,6 +450,13 @@ Examples
 
 This runs Jest v24.x in watch mode. See [https://jestjs.io](https://jestjs.io) for options. If you are using the React template, jest uses the flag `--env=jsdom` by default.
 
+If you would like to disable watch mode, this is one way to do it in your `package.json`:
+
+```
+"test": "CI=true tsdx test --color"
+"test:coverage": "CI=true tsdx test --color --coverage"
+```
+
 ### `tsdx lint`
 
 ```shell