docs: notes about building & testing for future contributions

Author: Guilherme Prezzi

CONTRIBUTING.md

@@ -14,13 +14,15 @@ Thank you for your contribution 🤗!
 # install dependencies
 yarn install
 
-# run the tests
-yarn test
-
 # build the library
 yarn build
+
+# run the tests
+yarn test
 ```
 
+> Note that you need to build the library first to run the e2e tests.
+
 ## Using `npm link` or `yarn link`
 
 In order to use the library locally on another project, you can use the `npm`|`yarn` link feature.