chore: update readme with new wording (#917)

Author: NathanFlurry

.github/media/icons/bolt-regular.svg

@@ -1,4 +1,6 @@
-# Testing
+# Contributing
+
+## Testing
 
 For now, only testing the outcome of running the CLI is supported. Before running tests, make sure that you have installed and started Docker. 
 
@@ -25,4 +27,4 @@ $ ./scripts/e2e-publish.ts
 5. ```bash
 $ yarn workspace @actor-core/cli run test
 ```
-   - Runs the tests for the CLI, which includes running the CLI (inside Docker) with different arguments and checking the output.
+   - Runs the tests for the CLI, which includes running the CLI (inside Docker) with different arguments and checking the output.