Feature Request: Add in more Unity Editor functionality to test plugin

[stowy]

We would love to make the Google Mobile Ads Unity plugin easier to test basic functionality and wiring in the Unity Editor, to save building and deploying to device every time you want to test your ads integration.

https://github.com/googleads/googleads-mobile-unity/pull/1025 is an example of adding some of this basic functionality.

We would welcome more contributions to add in this sort of functionality for the other ad formats, as well as extending it for more callbacks to help replicate more of the native behavior in Unity Editor.

If you want to start getting more involved with improving the Google Mobile Ads Unity plugin, here is a great place to start!