Proposal: Add autolinking support

[JeroenMols]

Investigate a community request to support autolinking on Android: #299

It seems like react native supports two kind of Android modules: Native Modules and Turbo Modules (still in development).

As the name implies, Turbo modules are faster to initialize which speeds up cold start of react native apps. However they are still under development, even though already introduced since react native 0.60.0.

While I couldn't find a conclusive answer on this, it seems like Turbo Modules don't support autolinking (yet?). So this means we have to make a choice between either:

• Keep the existing Turbo modules: makes our SDK faster to initialize, but slightly harder to integrate
• Move back to Native modules: makes our SDK slower to initialize, but easier to integrate

This PR follows the steps to create a Native Module and makes autolinking work for our react native SDK.

We're looking for community feedback/guidance on how to proceed on this.

Note: interestingly, Lottie react native uses the Native Module

[JeroenMols]

We've decided to stick to turbo modules for now as faster app initialization outweighs the easier integration (especially on the longer term)

In the future we may decide to revise this or to add auto linking support for Turbo Modules. (when that becomes possible)

[djMax]

are you sure that it's not autolinking now? Because if I add it to MainApplication.java, I get an error saying it has already been linked.